Jet-propelled swimmer's month at work (7)

I believe the answer is:

octopus

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'jet-propelled swimmer's month at work' is the definition.
I can't tell whether this definition defines the answer.

'month at work' is the wordplay.
'month' becomes 'Oct' (abbreviation for October).
'at' is a charade indicator (letters next to each other).
'work' becomes 'opus' (an opus is an artistic work).
'oct'+'opus'='OCTOPUS'

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(Other definitions for octopus that I've seen before include "Marine creature" , "Cephalopod with suckered tentacles" , "Creature with eight tentacles" , "Spineless creature" , "pernicious organisation" .)

I've seen this clue in The Sun.

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