Crossword Genius

Postal centre in Stockport attracts tramp who goes downhill fast (3,3)

Ross

I believe the answer is:

ski bum

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'tramp who goes downhill fast' is the definition.
'ski bum' can be an answer for 'tramp' (thesaurus). I am unsure of the rest of the definition.

I don't understand how the remainder of the clue works.

Can you help me to learn more?

I've seen this clue in The Telegraph.
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