Cut up diamonds with an adherent of Daesh? (9)
I believe the answer is:
dismember
'cut up' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
(Other definitions for dismember that I've seen before include "Separate limbs from the body" , "Cut the limbs from" , "Divide up (organisation)" , "Break up" , "Tear limb from limb" .)