They rig the markets for jewellery (5)
I believe the answer is:
rings
'for jewellery' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for rings that I've seen before include "phones" , "Bands for fingers" , "that may circle planet (not ours)" , "Small circles or bands for the finger" , "Spaces used for boxing" .)