Sharpen up the ports (5)

I believe the answer is:

strop

'sharpen' is the definition.
(stropping is a kind of sharpening)

'up the ports' is the wordplay.
'up' is a reversal indicator (in down clue: letters go upwards).
'ports' backwards is 'STROP'.

(Other definitions for strop that I've seen before include "Sharpen an old blade" , "Bad temper - sharpen (a razor)" , "Piece of leather on which razor is sharpened" , "wobbly" , "Prime cutthroat" .)

I've seen this clue in The Telegraph.

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