Singular spicy drink (4)
I believe the answer is:
shot
'drink' is the definition.
(I've seen this before)
'singular spicy' is the wordplay.
'singular' becomes 's' (abbreviation sometimes used in dictionaries).
'spicy' becomes 'hot' ('hot' can be a synonym of 'spicy').
's'+'hot'='SHOT'
(Other definitions for shot that I've seen before include "Knackered" , "Injection" , "Slug" , "Woven in different colours; attempt to score" , "glass of spirits" .)