Rock's ____ Clapton (4)
I believe the answer is:
eric
'rock's clapton' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for eric that I've seen before include ".... the Red, Norwegian explorer who discovered Greenland in 10th century" , "---- Roberts, actor brother of Julia" , "--, or Little by Little (Dean Farrar)" , "Man" , "Ernie's comic partner" .)