Current West End performance (3)
I believe the answer is:
act
'performance' is the definition.
(act is a kind of performance)
'current west end' is the wordplay.
'current' becomes 'actual' (similar in meaning).
'west end' indicates taking half (the half on the left or west).
'actual' halved is 'ACT'.
(Other definitions for act that I've seen before include "Take part in a play" , "Parliamentary decree" , "Start of a drama" , "Major division of play" , "Feign" .)