Hair treatment for hotheads? (5)

I believe the answer is:

singe

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'hair treatment' is the definition.
(I've seen this in another clue)

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

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(Other definitions for singe that I've seen before include "Burn slightly on surface" , "Lightly burn" , "Result of match accident" , "Result of burning" , "Scorch slightly on surface" .)

I've seen this clue in the Evening Standard.

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