Thread that only breaks when one of the ends is missing (5)
I believe the answer is:
nylon
'thread' is the definition.
(thesaurus)
'only breaks when one of the ends is missing' is the wordplay.
I cannot really see how this works, but
an anagram of 'only' is 'nylo' which is present in the answer.
A single letter 'n' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
'that' is the link.
Can you help me to learn more?
(Other definitions for nylon that I've seen before include "Plastic used for stockings" , "Man-made material" , "Hosiery material" , "Unaccompanied part song" , "where ladder can appear?" .)