Ring sandpiper (4)
I believe the answer is:
knot
I believe this is a double definition.
'ring' is the first definition.
(thesaurus)
'sandpiper' is the second definition.
(knot is a kind of sandpiper)
(Other definitions for knot that I've seen before include "Tie; sandpiper" , "Flier" , "Could be a granny or a sheepshank" , "Fastening formed by tying string etc" , "Ravel" .)