Sound made by piano technician? Something fishy here (4)
I believe the answer is:
tuna
'something fishy here' is the definition.
(tuna is a type of fish)
'sound made by piano technician?' is the wordplay.
'sound made by' shows a homophone (sound like).
'piano technician?' becomes 'tuner' (piano tuner).
'tuner' is a homophone of 'TUNA'.
(Other definitions for tuna that I've seen before include "Tunny" , "(Meat of) large fish" , "Fish sold in cans" , "Large edible sea fish, often canned" , "Species of fish" .)