Prime cut of beef (7)
I believe the answer is:
sirloin
'prime cut of beef' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sirloin that I've seen before include "(Knighted?) cut of meat" , "Prime cut of beef" , "Upper part of loin of beef" , "Good cut of beef" , "Joint of beef" .)