Guy handin’ out instrument (8)
I believe the answer is:
mandolin
'out instrument' is the definition.
'mandolin' can be an answer for 'instrument' (I've seen this before). I'm unsure of the 'out' bit.
'guy handin'' is the wordplay.
'guy' becomes 'man' (I've seen this before).
'handin'' becomes 'dolin' (I can't explain this - if you can you should believe this answer much more).
'man'+'dolin'='MANDOLIN'
(Other definitions for mandolin that I've seen before include "Stringed instrument, usually played with a plectrum" , "Round-backed musical instrument" , "it has strings attached" , "Plucked instrument" , "Small guitar-like instrument" .)