Cut some French opals (4)
I believe the answer is:
chop
'cut' is the definition.
(chop is a kind of cut)
'some french opals' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'CHOP' is hidden in the letters of 'french opals'.
(Other definitions for chop that I've seen before include "Thick slice of meat including rib" , "Cut - a piece of meat" , "Reduce drastically" , "Cut by blow of axe" , "Piece of meat - the sack" .)