What gardener may use to sing hit (5,3)

I believe the answer is:

grass box

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'what gardener may use' is the definition.
I can't tell whether this defines the answer.

'sing hit' is the wordplay.
'sing' becomes 'grass' (I've seen this before).
'hit' becomes 'box' (boxing is a kind of hitting).
'grass'+'box'='GRASS BOX'

'to' is the link.

Can you help me to learn more?

(Another definition for grass box that I've seen is " Attachment to mower".)

I've seen this clue in The Independent.

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