One maintaining pianos, you say? Something fishy here (4)
I believe the answer is:
tuna
'something fishy here' is the definition.
(tuna is a type of fish)
'one maintaining pianos you say?' is the wordplay.
I cannot really see how this works, but
'one' could be 'un' (northern English dialect form of 'one') and 'un' is found within the answer.
The remaining letters 'ta' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tuna that I've seen before include "Large sea-fish" , "(Meat of) large fish" , "Skipjack --, blue-fin --" , "Bluefin, e.g." , "Sea creature" .)