After performance, I have to be busy (6)
I believe the answer is:
active
'be busy' is the definition.
(similar in meaning)
'after performance i have' is the wordplay.
'after' means one lot of letters go next to another.
'performance' becomes 'act' (act is a kind of performance).
'i have' becomes 'I've' (contraction of 'I have').
'act' next to 'ive' is 'ACTIVE'.
'to' acts as a link.
(Other definitions for active that I've seen before include "Energetic, moving" , "(Of mind) alert, lively" , "Working; moving" , "In actual operation" , "Engaged, not idle" .)