Fasteners for jumpers (5)

I believe the answer is:

frogs

I'm a little stuck... Click here to teach me more about this clue!

'jumpers' is the definition.
(animals which jump)

'fasteners for' is the wordplay.
I cannot quite see how this works, but
an anagram of 'for' is 'fro' which is present in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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