Foil work, perhaps, putting up barriers (7)

I believe the answer is:

fencing

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'foil' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for fencing that I've seen before include "Olympic sport since 1896" , "Sport with swords" , "enclosure" , "Barrier; sport" .)

I've seen this clue in The Telegraph.

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