Thank you to Filbert. Definitions are underlined in the clues.
Across
1. Help Conservative to hide billions, moving account (3,5)
SOB STORY : [ SOS(an urgent appeal for help) + TORY(a member of the Conservative Party) ] containing(to hide) B(abbrev. for “billions”)
5. Departure for one on ship (6)
EGRESS : EG(abbrev. for “exempli gratia”/for example/for one) + RE(with reference to/on the subject of) + SS(abbrev. for “steamship”, used in the names of such).
10. Remote location for one affected their game (9)
HERMITAGE : Anagram of(affected) THEIR GAME.
Answer: Remote dwelling for one living in solitude/a hermit.
11. Oddball dismissed seconds from predicted retirement (5)
OUTRE : OUT(dismissed, as with a batsman in cricket) + respective 2nd letters of(seconds from) “predicted retirement”.
12. Carol never felt unlimited (4)
NOEL : NO(never) + “felt” minus its 1st and last letters(unlimited).
13. Trace of life left in Sackville-West’s grand garden? (5,5)
VITAL SPARK : VITA(Sackville-West, English author and garden designer)’S + PARK(what you might call a grand garden).
15. Running, shot and pole? My hero (5,8)
DALEY THOMPSON : Anagram of(Running) SHOT AND POLE? MY.
Answer: The English athlete who was World Champion in the decathlon, which event includes the shot put and pole vault A sporting hero.
18. Builder’s facing police officer, 100 mph in left lane (8,5)
PORTLAND STONE : [ DS(abbrev. for “Detective Superintendent”, a police officer) + TON(term for a speed of 100 mph) ] contained in(in) [ PORT(nautical term for the left side of a marine craft facing forwards) + LANE].
Answer: Material used by builders for the façade of buildings.
22. Prepare to deep-fry Mars bars for Spooner, whose utterances keep coming (10)
CHATTERBOX : Spoonerism of [ “batter”(to prepare to deep-fry by dipping in batter) “chocs”(short for “chocolates”, an example of which are Mars bars) ].
Defn: One ….
24. Bride arranged the setting for fantasy (4)
IDEA : Hidden in(… the setting for) “Bride arranged”.
26. Book to be collected by car, where you’re put on hold? (5)
LIMBO : B(abbrev. for “book”) contained in(to be collected by) LIMO(short for “limousine”, a large luxurious car).
Defn: An uncertain period in which you are put on hold awaiting a decision or resolution.
27. Since fish nets unavailable, one loses weight on ship (9)
ASTRONAUT : AS(since/because, as in “I can’t do it now as I’m busy”) + TROUT(a freshwater fish) containing(nets) NA(abbrev. for “not available”/unavailable).
Answer: One who becomes weightless by being in a spaceship far from the earth’s gravity.
28. Return wrong filling delivered for pastry (6)
DANISH : Reversal of(Return) [ SIN(a wrong/an offence) contained in(filling) HAD(gave birth to/delivered) ].
29. Foot part of insect eaten by cook (8)
INFANTRY : [ IN(be part of/within) + ANT(a social insect) ] contained in(eaten by) FRY(to cook in hot oil or fat).
Defn: That for which … is a historical term.
Down
1. Species, cross including head of human and every other bit of lion (6)
SPHINX : [ SP(abbrev. for “species”) + X(letter representing a cross) ] containing(including) 1st letter of(head of) “human” plus(and) 2nd and 4th letters of(every other bit of) “lion”.
Answer: In Greek mythology, a creature with the head of a human and the body of a lion and the wings of an eagle, hence a cross species.
2. Local worker saving money (9)
BARTENDER : BAR(with the exception of/saving) + TENDER(or legal tender/money that is part of the official currency of a country at a particular time).
Defn: …, ie. one working in a pub frequented by people living or working nearby.
3. Stick the rug down in Ilkley? (4)
TWIG : T’(“the” as it would be pronounced in the local dialect of Ilkley, Yorkshire, England) WIG(“rug” informally).
4. Try a lie to distort truth (7)
REALITY : Anagram of(… to distort) TRY A LIE.
6. Complain again, hearing that firing range after August 12th? (6,4)
GROUSE MOOR : GROUSE(to complain/grumble) homophone of(…, hearing that) “more”(again, as in “to fail once more”).
Defn: An area of moorland where red grouse are hunted and shot, the season for which starts on August 12th
7. Abandoned lover with skill climbing on top (5)
EXTRA : EX(former/abandoned lover) plus(with) reversal of(… climbing, in a down clue) ART(skill/knack at doing something).
Defn: …/in addition to.
8. Quietly interrupting naval chief, talk (8)
SPEAKING : P(abbrev. for “piano”, musical direction to play softly/quietly) contained in(interrupting) [SEA KING](what you might whimsically call a naval chief).
Answer: …, as a noun.
9. Work over, what remains after term for professor? (6)
REHASH : [ EH?(like “what?”, expressing a request for clarification or repetition of, or surprise at, what’s been said) + AHS(remains after burning) ] placed after(after) last letter of(term for/completion of) “professor”.
14. Eurovision winner, upset country’s losing lead, wails (10)
ULULATIONS : Reversal of(…, upset, in a down clue) LULU(Sottish singer who represented the UK in, and won the Eurovision Song Contest in 1969 with “Boom Bang-A-Bang”) + “nation’s”(country’s/state’s) minus its 1st letter(losing lead).
Answer: Vocal sounds like howls/wails involving rapid movement of the tongue and uvula.
16. Constant force cracks nuts as stated (9)
STEADFAST : F(symbol for “force” in physics) contained in(cracks) anagram of(nuts) AS STATED.
17. Spotty son managed to bag kiss (8)
SPECKLED : [ S(abbrev. for “son”) + LED(ran/managed, say, an organisation) ] containing(to bag) PECK(a light kiss).
19. Land with many inlets, as if cut by river (6)
NORWAY : [NO WAY!](like “as if!”, an expression of disbelief) containing(cut by) R(abbrev. for “river”).
Defn: …/fjords.
20. Dock‘s our standard base behind seafront, mostly (7)
SHORTEN : TEN(the numerical base for the decimal system, our standard numbering system, using digits 0 to 9) placed after(behind) “shore”(the seafront/seaside) minus its last letter(mostly).
Defn: …/to cut off the tip of, say, a dog’s tail.
21. Mean person you’d be pleased to see go (6)
PALTRY : PAL(friend, a person you’d be pleased to see/meet) + TRY(go/one’s turn to do something, say, during a multiplayer game).
Defn: …/of very small amount.
23. African dictator smuggling diamonds, mundane business (5)
ADMIN : AMIN(Idi, former African dictator) containing(smuggling) D(symbol for the suit of diamonds in a deck of playing cards).
Answer: Short for “administration”, which I suppose could be mundane most of the time.
25. Large item from IKEA perhaps unfinished until now (4)
SOFA : Last letter of(unfinished) “so far”(up to this moment/until now).