Took part, having excellent day — about time (5)
I believe the answer is:
acted
'took part' is the definition.
'excellent day about time' is the wordplay.
'excellent' becomes 'ace' (I've seen this before).
'day' becomes 'd' (abbreviation for day).
'about' is an insertion indicator.
'time' becomes 't' (abbreviation).
'ace'+'d'='aced'
'aced' enclosing 't' is 'ACTED'.
'having' acts as a link.
(Other definitions for acted that I've seen before include "Posed as" , "Behaved or played a part" , "Pretended" , "Play a role" , "Performed on stage" .)