By the sound of it, tool fixed (6)

I believe the answer is:

spayed

'fixed' is the definition.
(fix can mean to spay an animal)

'by the sound of it tool' is the wordplay.
'by the sound of it' shows a homophone (sound like).
'tool' becomes 'spade' (spade is a kind of tool).
'spade' sounds like 'SPAYED'.

(Another definition for spayed that I've seen is " Unable to produce".)

I've seen this clue in The Guardian.

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