Couple to allow some jewellery (8)
I believe the answer is:
bracelet
'some jewellery' is the definition.
(bracelet is a kind of jewellery)
'couple to allow' is the wordplay.
'couple' becomes 'brace' (brace can mean a pair of something).
'to allow' becomes 'let' ('let' can be a synonym of 'allow').
'brace'+'let'='BRACELET'
(Other definitions for bracelet that I've seen before include "Arm band" , "Wrist, arm adornment" , "Might Bel react badly to this jewellery?" , "Item of jewellery found in Crete lab" , "16 [ADORNMENT]" .)