Duffel coat fastener (6)
I believe the answer is:
toggle
'duffel coat fastener' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for toggle that I've seen before include "Wooden pin" , "Coat fastener; computer switch" , "Fastener; type of switch" , "Fastening eg for Paddington's coat" , "Type of fastening - on/off key" .)