About to carve ham (7)
I believe the answer is:
overact
'ham' is the definition.
('overact' can be a synonym of 'ham')
'about to carve' is the wordplay.
'about' is an anagram indicator.
'to'+'carve'='tocarve'
'tocarve' is an anagram of 'OVERACT'.
(Other definitions for overact that I've seen before include "pile it on" , "Be excessive like fulsome thespian" , "Perform hammily" , "Exaggeratedly perform a role" , "Ham (on stage)" .)