Run in a stocking (6)
I believe the answer is:
ladder
'run in a stocking' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ladder that I've seen before include "Run in stockings" , "Vertical run in tights" , "Domestic device for climbing" , "A fire-fighter may use one" , "Climbing steps or rungs" .)