Scientist on holiday entering wine store (6)
I believe the answer is:
boffin
'scientist' is the definition.
(boffin is a kind of scientist)
'on holiday entering wine store' is the wordplay.
'on holiday' becomes 'off' (I've seen this before).
'entering' is an insertion indicator.
'wine store' becomes 'bin' (stand for storing wine bottles).
'off' placed inside 'bin' is 'BOFFIN'.
(Other definitions for boffin that I've seen before include "Scientist (in the back room?)" , "Brainbox" , "Back-room boy" , "Technical expert" , "(Government) scientist" .)