About to act or play the ham (6)
I believe the answer is:
overdo
'or play the ham' is the definition.
I can't tell whether this definition defines the answer.
'about to act' is the wordplay.
'about' becomes 'over' (both can mean around).
'to act' becomes 'do' (to do is to act or execute a task).
'over'+'do'='OVERDO'
Can you help me to learn more?
(Other definitions for overdo that I've seen before include "Exhaust" , "Put too much effort into" , "Perform excessively" , "Use too much of (something)" , "Exaggerate, go too far" .)