I found this fairly straightforward. Solving time: 15 mins.
(LATER: there is a Nina here that I missed though I did look, but another has pointed it out. I refer to it after the clue explanations.)
* = anagram
ACROSS
1 LECTIONARY (not clear I)* y = last of early A book of church lessons for each day.
6 JAVA First letters, indicated by “initially”
10 GA(E)L DO M Do = party M = male
11 S (TERN) UM
12 CO (PART) NE R
13 VAL(V)E depression = valley = vale
14 F (RAN) C ‘No longer’ as franc has been replaced as French currency by the euro.
15 EDELWEISS (lies weeds)*
21 GAFFE(r)
25 TRANC (H) E
26 Bertie WOOS TER(m)
27 (b)RAKE Reasonably obscure form of transport
28 S(T)AN DER (S) – BY San = Sanitorium = hospital
DOWN
2 C HEAP JACK
7 ANNU (a) L annual is last word in last clue (24 down)
9 LEAVE WELL ALONE Liked that – cryptic definition of phrase.
19 TH (ROW) – IN Wondered about ‘pause’ as a definition – I imagined the physio coming on, then light dawned.
22 FL (abbrev) ASK
24 (y)EARLY unknowns from equations can be x, y or z
Theme: look in row 6, cf 26 across!
Good as always from Phi. Have to quibble with the definition for 6A though: “website tool”. JAVA is a development/programming language; you might be able to make website tools with it (amongst many other things – applications for mobile phones perhaps) but surely that doesn’t make it the same thing?
I agree, excellent as always. There are a few setters (in particular Virgilius, Dac, Phi) whose clues are consistently sound but simple in construction and pithy with good surfaces.
10A (VALVE) was particularly good, I thought.
Unknowns
Another thing I meant to say. In the post for 24D, nmsindy says “unknowns from equations can be x, y or z”. Or any letter, really, although these are the most usual. I never like it when z is called an unknown, as if it’s of the same type as x or y. It’s used (almost exclusively?) for complex numbers, which are hardly mainstream.
Wil on unknowns: The Concise Oxford has x/y/z defined as the first/second/third unknowns in an algebraic expression. I think this is the reason for the ‘X, Y or Z’ convention. We’re probably talking old-fashioned algebra here – there are examples fitting the bill in my copy of Hall & Knight’s Elementary Algebra (revised 1907) which I’m pretty sure was the standard text in its day – see this poem.
Yes, what Peter says is the same as my experience both with algebra (in days gone by) and doing puzzles over the years. y was used in the Phi puzzle. My view of complex numbers is, like Wil, that they are “hardly mainstream” and I’ve not seen them referred to in puzzles that I can recall.