Hammy actor with dilemma performing (12)
I believe the answer is:
melodramatic
'hammy' is the definition.
(thesaurus)
'actor with dilemma performing' is the wordplay.
'with' is a charade indicator (letters next to each other).
'performing' indicates an anagram.
'actor' after 'dilemma' is 'dilemmaactor'.
'dilemmaactor' anagrammed gives 'MELODRAMATIC'.
(Other definitions for melodramatic that I've seen before include "Exaggerated - over-emotional" , "like ham?" , "Emotionally overblown (in theatre)" , "Sensational" .)