Can I spoil first drink (7)
I believe the answer is:
martini
'drink' is the definition.
(martini is a kind of drink)
'can i spoil first' is the wordplay.
'can' becomes 'tin' (both are metal containers).
'spoil' becomes 'mar' (synonyms).
'first' means one lot of letters go next to another.
'tin'+'i'='tini'
'tini' after 'mar' is 'MARTINI'.
(Other definitions for martini that I've seen before include "alcoholic drink" , "Type of Italian vermouth" , "rifle" , "Italian drink" , "Sienese painter" .)