On some days, sailors do their mending (4)

I believe the answer is:

darn

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'do their mending' is the definition.
I can't judge whether this defines the answer.

'on some days sailors' is the wordplay.
'on' says to put letters next to each other.
'some' becomes 'a'.
'days' becomes 'd'.
'sailors' becomes 'rn' (abbreviation for Royal Navy).
'a' after 'd' is 'da'.
'da'+'rn'='DARN'

Can you help me to learn more?

(Other definitions for darn that I've seen before include "Mend (knitted material)" , "Repair by sewing, socks perhaps" , "Repair (with needle)" , "Mend with a needle" , "Stitch" .)

I've seen this clue in the Evening Standard.

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