Clark up on the roof? (5)
I believe the answer is:
gable
This clue is a double definition.
'clark' is the first definition.
(actor Clark Gable)
'up on the roof?' is the second definition.
(feature of a roof)
(Other definitions for gable that I've seen before include "Roof structure" , "Side of house or Clark, film star" , "Filmstar at the side of the house?" , "End of a house" , "US actor" .)