Ruin unloved folk instrument with interminable rock guitar (6)
I believe the answer is:
banjax
'ruin' is the definition.
(I've seen this before)
'unloved folk instrument with interminable rock guitar' is the wordplay.
I cannot really see how this works, but
'instrument' could be 'ban' (ban is a kind of instrument) and 'ban' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for banjax that I've seen before include "Incapacitate" , "Destroy, ruin, damage" , "Ruin (informal)" , "wreck" .)