The Rock screens lead role (4)
I believe the answer is:
hero
'lead role' is the definition.
(thesaurus)
'the rock screens' is the wordplay.
'screens' indicates the answer is hidden within the clue.
'HERO' can be found hidden inside 'the rock'.
(Other definitions for hero that I've seen before include "Man admired for courage and nobility" , "Person renowned for bravery" , "eg Achilles" , "Admired champion" , "Man of outstanding courage" .)