French writer switching characters shows courage (5)

I believe the answer is:

nerve

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'courage' is the definition.
(I know that nerve is a type of courage)

I don't understand the rest of the clue.

(Other definitions for nerve that I've seen before include "displaying self-possession" , "Bundle of fibres < in face" , "Fibre that transmits instructions to the brain" , "Dangerous type of gas" , "Coolness under fire" .)

I've seen this clue in The Telegraph.

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