Sharp beer resident emptied (5)
I believe the answer is:
alert
'sharp' is the definition.
('alert' can be a synonym of 'sharp')
'beer resident emptied' is the wordplay.
'beer' becomes 'ale' (I've seen this before).
'emptied' means to remove the middle letters.
'resident' with its middle taken out is 'rt'.
'ale'+'rt'='ALERT'
(Other definitions for alert that I've seen before include "Signal danger" , "Wakeful, observant" , "Lively" , "Prompt" , "'Attentive, watchful (5)'" .)