Start of holiday in pleasant nook (5)
I believe the answer is:
niche
'nook' is the definition.
(I've seen this before)
'start of holiday in pleasant' is the wordplay.
'start of' indicates taking the first letters.
'in' indicates putting letters inside.
'pleasant' becomes 'nice' (similar in meaning).
The initial letter of 'holiday' is 'h'.
'h' put inside 'nice' is 'NICHE'.
(Other definitions for niche that I've seen before include "Calling" , "Small recess or cranny" , "small specialised market" , "Suitable slot" , "ideal position" .)