Bet Clare smashed piece of jewellery (8)
I believe the answer is:
bracelet
'piece of jewellery' is the definition.
(I've seen this before)
'bet clare smashed' is the wordplay.
'smashed' indicates an anagram.
'bet'+'clare'='betclare'
'betclare' anagrammed gives 'BRACELET'.
(Other definitions for bracelet that I've seen before include "Ornament worn on arm or wrist" , "Rebel cat (anag.)" , "16 [ADORNMENT]" , "Arm band" , "Ornament - handcuff (slang)" .)