Stop a single Rocky star (8)
I believe the answer is:
stallone
'rocky star' is the definition.
(I've seen this in another clue)
'stop a single' is the wordplay.
'stop' becomes 'stall' (stalling is a kind of stopping).
'a single' becomes 'one' (a single thing - only one).
'stall'+'one'='STALLONE'
(Other definitions for stallone that I've seen before include "Sylvester - (Rambo)" , "See 6" , "Sylvester -, US actor" , "Hollywood actor" , "Sylvester ........, Hollywood tough guy" .)