Nerve - but not of steel (5)

I believe the answer is:

brass

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

'nerve' is the definition.
(I know that nerve can be written as brass)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for brass that I've seen before include "Alloy of Cu and Zn" , "An alloy; part of orchestra" , "Impertinence" , "Alloy (associated with muck)" , "Alloy; money" .)

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

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