Instrument for tinker (6)
I believe the answer is:
I believe this is a double definition.
'instrument' is the first definition.
(I know that fiddle is a type of bowed stringed instrument)
'for tinker' is the second definition.
(I've seen this before)
(Other definitions for fiddle that I've seen before include "Stringed instrument - cheat" , "Cheat using violin" , "Trifle - swindle" , "Sham" , "The poor man's violin" .)