Very enjoyable and on the whole not too difficult, just a couple that I struggled with. Thank you Aardvark.
| Across | ||
| 1 | MIXED DOUBLES | Tennis match is repeated on compound (5,7) | 
| DOUBLES (is repeated) following (on) MIXED (compound) | ||
| 10 | URANIUM | Posh auntie regularly in company of peculiar element (7) | 
| U (posh) and AuNtIe (regular selection of) in RUM (odd) | ||
| 11 | SULTANA | Articles on lust involved mistress abroad (7) | 
| AN A (articles) on LUST* anagram=involved- a sultan’s concubine | ||
| 12 | RAISE | Noisily demolish hoist (5) | 
| sounds like (noisily) raze (demolish) | ||
| 13 | FORELIMB | Retired British middle-distance runner belonging to section of body (8) | 
| B (British) MILER (middle distance runner) OF (belonging to) all reversed (retired) | ||
| 15 | EASY STREET | Yankee’s large plant in the Orient offers financial security (4,6) | 
| Y’S (yankee’s, phonetic alphabet) and TREE (large plant) in EAST (the Orient) | ||
| 16 | DADO | Wooden border finally completed with difficulty (4) | 
| D (final letter of completed) with ADO (difficulty) – a decorative wooden border | ||
| 18 | MARL | Fertiliser left on soil (4) | 
| L (left) following (on) MAR (soil) | ||
| 20 | CEREMONIAL | Official day one enters porridge? (10) | 
| MON (day) I (one) in (enters) CEREAL (porridge) | ||
| 22 | SPORADIC | Occasional trailer one’s seen among produce being brought back (8) | 
| AD (tailer) I (one) in (seen among) CROPS reversed | ||
| 24 | SALEM | Proposal emerged to ring-fence American capital (5) | 
| in (ringfenced by) propoSAL EMerged – capital of Oregon | ||
| 26 | ERODING | Dicky ignored eating away (7) | 
| IGNORED* anagram=dicky` | ||
| 27 | DRAYMEN | In Scotland, they carry heavy fish miles into hideaway (7) | 
| RAY (fish) M (miles) in DEN (hideaway) – drivers of Brewery wagons, possibly carrying Heavy (70 shilling ale in Scotland) | ||
| 28 | TRUMPET MAJOR | Musician and tenor drink with beloved prime minister earlier (7,5) | 
| T (tenor) RUM (drink) with PET (beloved) MAJOR (John, former PM) | ||
| Down | ||
| 2 | ITALICS | Characters that lean, showing stress (7) | 
| cryptic definition | ||
| 3 | EPILEPSY | Lots to enter recording Sandy’s disheartening medical condition (8) | 
| PILE (lots) in (to enter) EP (extended play, recording) then SandY (disheartened, no middle letters) | ||
| 4 | DUMB | Stupid name, admits head of marketing (4) | 
| M (first letter of marketing) in DUB (name) | ||
| 5 | UNSHOWERED | Perhaps dirty appearance evident in a French claret (10) | 
| SHOW (appearance) inside (evedent in) UNE (a, French) RED (claret) | ||
| 6 | LILLE | European city, centre of excellence in fabrication (5) | 
| exceLLence (centre of) in LIE (fabrication) | ||
| 7 | STAMINA | Upstairs, a rug’s caught in the legs (7) | 
| A MAT’S (rug’s) reversed (upstairs) containing (caught) IN – definition is ‘the legs’.  I am not convinced ‘upstairs’ means ‘upside-down’.    | 
||
| 8 | QUARTERMASTER | Naval officer bearing defeat (13) | 
| QUARTER (bearing, of compass) MASTER (defeat) | ||
| 9 | BAMBOOZLEMENT | Tree unknown, first leaving mild confusion (13) | 
| BAMBOO (tree) Z (unknown, often used in maths) cLEMENT (mild) missing first letter | ||
| 14 | CREEPING UP | Native American to restrain upset dog, advancing slowly (8,2) | 
| CREE (Native American) PIN (to restrain) PUG (dog) reversed (upset) | ||
| 17 | BOTSWANA | Snake stifles source of trouble, aquatic bird in south Africa (8) | 
| BOA (snake) contains (stifles) T (first letter of trouble) SWAN (aquatic bird) | ||
| 19 | ROOT OUT | Eradicate bounder who trades aggressively (4,3) | 
| ROO (kangaroo, bounder) TOUT (aggressive trader) | ||
| 21 | IN LIMBO | At home, bones put in cooking fat, turning on the back burner (2,5) | 
| IN (at home) then MB (doctor, bones) in OIL (cooking fat) reversed (turning) | ||
| 23 | ADIEU | The German’s covered in gold for farewell (5) | 
| DIE (the, German) in AU (gold, chem symbol) | ||
| 25 | EDIT | Correct time showed up (4) | 
| TIDE (time) reversed (showed up) | ||
*anagram
I think in 5d it’s UNE not UN.
So it is! Fixed now.
Thanks PeeDee and Aardvark – good stuff.