High beef rating (5)
I believe the answer is:
prime
'high beef rating' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for prime that I've seen before include "Prepare for use, say a pump" , "Number with no factor but itself and 1" , "Chief or most important, like a minister" , "Best - get ready" , "Main - charge" .)