Gate returns may depend on its smooth operation (5)

I believe the answer is:

hinge

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'operation' is the definition.
The definition and answer can be both states of affairs as well as being singular nouns.
Maybe there's a link between them I don't understand?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for hinge that I've seen before include "Joint on which something turns" , "Flexible joint" , "Movable swinging joint" , "On what a door swings" , "Moveable joint" .)

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

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