It's as strong as its weakest link (5)
I believe the answer is:
chain
'it's as strong as its weakest link' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for chain that I've seen before include "unwelcome to house seeker" , "group of shops here" , "Connected sequence" , "Set of links" , "Mountain range" .)