Guard seen changing into work gear (9)

I believe the answer is:

dungarees

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'into work gear' is the definition.
I can't judge whether this definition defines the answer.

'guard seen changing' is the wordplay.
'changing' is an anagram indicator.
'guard'+'seen'='guardseen'
'guardseen' anagrammed gives 'DUNGAREES'.

Can you help me to learn more?

(Other definitions for dungarees that I've seen before include "Worker's trousers with a bib" , "protection at work" , "overalls required" , "Hard-wearing work trousers with a bib" , "garment" .)

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

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