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" .)