Some anxious to please in bar (4)
I believe the answer is:
stop
'bar' is the definition.
(I know that bar can be written as stop)
'some anxious to please' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'STOP' is hidden within 'anxious to please'.
'in' acts as a link.
(Other definitions for stop that I've seen before include "cut out" , "Red light signal" , "high card in bridge" , "Withhold payment" , "as per instruction" .)