Wide awake right after drink (5)
I believe the answer is:
alert
'wide awake' is the definition.
(I've seen this in another clue)
'right after drink' is the wordplay.
'right' becomes 'rt' (abbreviation as in Rt Hon- the Right Honourable).
'after' is a charade indicator (letters next to each other).
'drink' becomes 'ale' (type of beer).
'rt' after 'ale' is 'ALERT'.
(Other definitions for alert that I've seen before include "Put on guard, warn" , "Watchful and bright" , "Watchful; warning" , "Wakeful, observant" , "Warning signal" .)