Fifteensquared

Plenty of Flimsy whimsy in evidence today, although I thought that a couple of clues (12A, 19A) were, in part, too lazily self-referential.  On the plus side, I learned a geographic factoid courtesy of fact-checking the clue to 10A.

Across
1 WINDJAMMER - wind + jam me + r{uddy}.
4 DEFT - ed< + FT.
9 THAI - hidden.
10 IRRELEVANT - (River Lena)* + t[emperature].  Apparently the Lena is the 11th longest river in the world.  Perhaps it should consider hiring a better PR agent?
11 WRITER - homophone of “right”+ r[uns].
12 EYEGLASS – eye + G + lass.
13 STRIKING - double def’n.
15 PEER - pee + R. ‘Go’ in the lavatorial sense.
17 ORAL - {m}oral.
19 RESCRIPT - re: + script.
22 GANGRENE - gang + René.
23 AFLOAT - a[cccepted] + float.
25 FIELD TRIPS – field + trips.  Twenty years on, I’m still haunted (“tor”mented?) by scholastic memories of a couple of days of investigating the storm-swept terrain of Dartmoor – all in the name of GCSE Geography.
26 NEED - need{le}.
27 DENY - Ned< + y[ard].
28 ENGINE ROOM - E[nergy] +g[ood] in (in Rome)*.

Down
2 INHERIT - (in the IR)*.  A little indirectness in the anagram fodder, but I’m willing to indulge it for the concise/coherent surface.
3 DRIFT- d{runk} + rift.
4 ACID RAIN - cryptic def’n.  Although it read very transparently to me.
5 MARKET GARDENING - (danger)* in marketing. In the US, a market garden is known (far more prosaically) as a truck farm.
6 ROLLER - double def’n.
7 DEVELOPER - (deep love)* + R[esistance].  This one raised the biggest smile, so is the de facto clue of the day.
8 FINESSE - (Essen + if)*.
14 ILLEGALLY - ill + galley, with the e promoted.
16 ASSASSIN - ass x2 + ni{b}<.
18 REALISE - (See rail)*.
20 PLACEBO - place + B.O. (there’s been a lot of this in the air recently, it seems).
21 SEETHE - see + het*.
24 LINER - (Nile)* + r.