Fastener apt to give way?
I believe the answer is:
buckle
'give way?' is the definition.
(buckling is a kind of giving way)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for buckle that I've seen before include "Crumple under pressure, like shoe clasp" , "Crumple under pressure, or belt fastener" , "Give way to pressure" , "Collapse under pressure" , "It's attached to a belt or shoe" .)