Couple hire piece of jewellery (8)
I believe the answer is:
bracelet
'piece of jewellery' is the definition.
(I've seen this before)
'couple hire' is the wordplay.
'couple' becomes 'brace' ('brace' can be a synonym of 'couple'**).
'hire' becomes 'let' (I've seen this in other clues).
'brace'+'let'='BRACELET'
(Other definitions for bracelet that I've seen before include "Item of jewellery on wrist" , "Ornamental band worn on wrist" , "Ornamental wristband" , "Jewellery worn around the wrist" , "Wrist, arm adornment" .)