Bowline or clove hitch (4)
I believe the answer is:
knot
I believe this clue is a double definition.
'bowline' is the first definition.
(I've seen this in another clue)
'clove hitch' is the second definition.
(I know that clove hitch is a knot)
(Other definitions for knot that I've seen before include "Assemblage" , "Measure of speed on water" , "Shore bird; cluster" , "Could be a granny or a sheepshank" , "Nautical speed - group of toads" .)