Do behave (3)
I believe the answer is:
act
I believe this clue is a double definition.
'do' is the first definition.
(thesaurus)
'behave' is the second definition.
(acting is a kind of behaving)
(Other definitions for act that I've seen before include "law passed" , "Aussie parliamentarians exert influence here?" , "Parliamentary decree" , "Pretend to be - deed" , "Function" .)