Clothesline fastener (3)
I believe the answer is:
peg
'clothesline fastener' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for peg that I've seen before include "Wooden or plastic pin for hanging clothes" , "Clip for hanging washing" , "Small dowel" , "Kind of clip for fastening clothes to line" , "The girl to hang your hat on" .)