A restraining habit (12)

I believe the answer is:

straitjacket

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'habit' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe you can see a link between them that I don't see?

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for straitjacket that I've seen before include "restraint" , "restriction" , "Restraining garment" , "Garment used to restrain people" .)

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

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