Clark's big role (5)
I believe the answer is:
rhett
'clark's big role' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rhett that I've seen before include "..... Butler was Scarlett O'Hara's lover" , "Scarlett O'Hara's lover-husband ..... Butler" , "Hero of the above" .)