Bully, in reality, ran theatre (6)
I believe the answer is:
tyrant
'bully' is the definition.
(I've seen this before)
'in reality ran theatre' is the wordplay.
'in' says the answer is hidden in the clue.
'TYRANT' can be found hidden inside 'reality ran theatre'.
(Other definitions for tyrant that I've seen before include "Despotic ruler" , "Authoritarian" , "Harsh and absolute ruler" , "Cruel and oppressive dictator" , "Arbitrary ruler" .)