Call on horse farm for fastener (5,4)

I believe the answer is:

press stud

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'fastener' is the definition.
(press stud is a kind of fastener)

'call on horse farm' is the wordplay.
'call on horse' becomes 'press' (I can't explain this - if you can you should give a lot more credence to this answer).
'farm' becomes 'stud' (stud farm is a kind of farm).
'press'+'stud'='PRESS-STUD'

'for' acts as a link.

Can you help me to learn more?

(Other definitions for press stud that I've seen before include "catch!" , "Snap fastener" , "Small fastener" , "Virile young editor, perhaps" , "It may secure clothing" .)

I've seen this clue in the Sydney Morning Herald.

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