If you want stiffening, have a couple! (5)

I believe the answer is:

brace

I'm a little stuck... Click here to teach me more about this clue!

'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 "prepare for impact" , "Pair - wood-boring tool" , "hand tool" , "Pair - strut" , "double" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app