Stay normal — head off for a drink (8)
I believe the answer is:
beverage
'a drink' is the definition.
('beverage' can be a synonym of 'drink')
'stay normal head off' is the wordplay.
'stay' becomes 'be' (stay can mean to continue to be a certain way).
'normal' becomes 'average' (synonyms).
'head off' means to remove the first letter.
'average' with its initial letter taken away is 'verage'.
'be'+'verage'='BEVERAGE'
'for' acts as a link.
(Other definitions for beverage that I've seen before include "Any drink, say a beer" , "Liquid refreshment" , "such as a Frappuccino" , "Liquid for drinking" , "Tea, say" .)