Steep climbs with number on crew who can deliver (9)

I believe the answer is:

postwoman

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'can deliver' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'steep climbs with number on crew' is the wordplay.
'steep' becomes 'sop' (both can mean to submerge in liquid).
'climbs' is a reversal indicator.
'with' means one lot of letters go next to another.
'number on' becomes 'two' (two is a kind of whole number. I am not sure about the 'on' bit.).
'crew' becomes 'man' (both can mean to staff or operate something).
'sop' written backwards gives 'pos'.
'pos'+'two'+'man'='POSTWOMAN'

'who' acts as a link.

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I've seen this clue in The Guardian.

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