Bend to fasten shoe, perhaps (6)
I believe the answer is:
buckle
'bend' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for buckle that I've seen before include "Fasten up - give way" , "Crumple under pressure, or belt fastener" , "It's attached to a belt or shoe" , "Catch" , "Bend out of shape" .)