Sign of fear here though singularly daring (6)

I believe the answer is:

nerves

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

'sign of fear' is the definition.
'nerves' can be an answer for 'fear' (thesaurus). I am not certain of the 'sign of' bit.

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

Can you help me to learn more?

(Other definitions for nerves that I've seen before include "Fibres carrying impulses around the body" , "causing some anxiety" , "Bodily fibres conveying sensations" , "Fibres that convey feelings" , "Apprehensive feeling" .)

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

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