Wretch's fall gardening tool's upgrading (5,8)

I believe the answer is:

rakes progress

I'm a little stuck... Click here to teach me more about this clue!

'wretch's fall gardening' is the definition.
I can't tell whether this defines the answer.

'tool's upgrading' is the wordplay.
'tool's' becomes 'rake's' (rake is a kind of tool).
'upgrading' becomes 'progress' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'rakes'+'progress'='RAKES PROGRESS'

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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