Line-shortening knot (10)
I believe the answer is:
sheepshank
'line-shortening knot' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sheepshank that I've seen before include "PS He has Ken (anag) -- rope-shortening knot" , "Cut of meat" , "It's not without hitches" , "[KNOT] - with 23a" , "Knot used to shorten a rope temporarily" .)