Hot in pleasant alcove (5)
I believe the answer is:
niche
'alcove' is the definition.
(I've seen this before)
'hot in pleasant' is the wordplay.
'hot' becomes 'h'.
'in' means one lot of letters goes inside another.
'pleasant' becomes 'nice' ('nice' is associated in meaning with 'pleasant').
'h' inserted within 'nice' is 'NICHE'.
(Other definitions for niche that I've seen before include "Small recess or cranny" , "good spot!" , "Specialised corner of the market" , "Specialist area" , "Place that's cosy" .)