Fix the piano, for instance (3)
I believe the answer is:
peg
'fix' is the definition.
(to fix or attach with a peg)
'piano for instance' is the wordplay.
'piano' becomes 'p' (musical abbreviation).
'for instance' becomes 'eg' (short for 'exempli gratia', 'for example' in Latin).
'p'+'eg'='PEG'
'the' is the link.
(Other definitions for peg that I've seen before include "Clothes line pin" , "Projecting pin" , "Wooden pin, small marker" , "Kind of clip for fastening clothes to line" , "Old song: ''... o' my heart''" .)