Come about act available (4,3)
I believe the answer is:
turn out
'come about' is the definition.
(turning out is a kind of coming about)
'act available' is the wordplay.
'act' becomes 'turn' (theatre**).
'available' becomes 'out' (I've seen this in other clues).
'turn'+'out'='TURN-OUT'
(Other definitions for turn out that I've seen before include "parade" , "Dismiss" , "Eventually appear" , "Prove" , "End up" .)