Tool starts to rust (always kept externally) (4)

I believe the answer is:

rake

'tool' is the definition.
(rake is a kind of tool)

'starts to rust always kept externally' is the wordplay.
'starts to' says to take the initial letters.
The first letters of 'rust always kept externally' is 'RAKE'.

(Other definitions for rake that I've seen before include "Leaves collector" , "Gardening tool for the dissolute fellow" , "I have bad habits" , "He made progress" , "One with teeth" .)

I've seen this clue in The Independent.

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