Give firmness to a couple (5)

I believe the answer is:

brace

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'to a couple' is the definition.
(brace can mean a pair of something)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for brace that I've seen before include "Strengthener; pair" , "hand tool" , "Pair - strut" , "Strengthening piece" , "Steady; pair" .)

I've seen this clue in The Irish News.

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