Talk about end of valuable fiddle (5)
I believe the answer is:
cheat
'fiddle' is the definition.
(thesaurus)
'talk about end of valuable' is the wordplay.
'talk' becomes 'chat' (I've seen this before**).
'about' means one lot of letters goes inside another.
'end of' says to take the final letters.
The final letter of 'valuable' is 'e'.
'chat' going around 'e' is 'CHEAT'.
(Other definitions for cheat that I've seen before include "Welsh" , "Act dishonestly to gain an advantage" , "Deceive, defraud" , "Deceitful person" , "22 [FRAUDSTER]" .)