Cut a piece of meat - quickly! (4-4)
I believe the answer is:
chop-chop
'quickly' is the definition.
(I've seen this before)
'cut a piece of meat' is the wordplay.
'cut' becomes 'chop' (chopping is a kind of cutting).
'a piece of meat' becomes 'chop' (e.g. a lamb chop).
'chop'+'chop'='CHOP-CHOP'
(Other definitions for chop-chop that I've seen before include "Hurry up!" , "Quickly!" , "Get a move on!" .)