Couple allowed jewellery (8)
I believe the answer is:
bracelet
'jewellery' is the definition.
(bracelet is a kind of jewellery)
'couple allowed' is the wordplay.
'couple' becomes 'brace' (brace can mean a pair of something).
'allowed' becomes 'let' (to let is to allow or permit).
'brace'+'let'='BRACELET'
(Other definitions for bracelet that I've seen before include "Rebel cat (anag.)" , "Might Bel react to the piece of jewellery?" , "Personal ornament" , "Let caber be made into a piece of jewellery" , "Item of jewellery found in Crete lab" .)