Ham open employing a can-opener? (7)
I believe the answer is:
overact
'ham' is the definition.
(synonyms)
'open employing a can-opener?' is the wordplay.
'open' becomes 'overt' (synonyms).
'employing' indicates putting letters inside.
'opener?' says to take the initial letters (I've seen 'opener' mean this).
The first letter of 'can' is 'c'.
'a'+'c'='ac'
'overt' placed around 'ac' is 'OVERACT'.
(Other definitions for overact that I've seen before include "In part, fail to convince" , "Be excessive like fulsome thespian" , "Play part exaggeratedly" , "Be unsubtle on stage" , "Do what ham thespian does" .)