Upright fellows working six days a week (7)

I believe the answer is:

postmen

I'm a little stuck... Click here to teach me more about this clue!

'working six days a week' is the definition.
I can't tell whether this defines the answer.

'upright fellows' is the wordplay.
'upright' becomes 'post' (upright can mean a vertical post).
'fellows' becomes 'men' (fellow can mean a man).
'post'+'men'='POSTMEN'

Can you help me to learn more?

(Other definitions for postmen that I've seen before include "They deliver mail" , "Mail deliverers" , "Male mail carriers" .)

I've seen this clue in the Evening Standard.

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