At times, working twice over shoes frayed at edges (2,8)

I believe the answer is:

on occasion

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'working twice over shoes frayed at edges' is the definition.
I can't judge whether this defines the answer.

'at times' is the wordplay.
'at' becomes 'on' (location).
'times' becomes 'occasion' (I can't explain this - if you can you should believe this answer much more).
'on'+'occasion'='ON OCCASION'

Can you help me to learn more?

(Another definition for on occasion that I've seen is " Sometimes".)

I've seen this clue in The Hindu.

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