Undercover agent's hidden temper (4)

I believe the answer is:

rage

'temper' is the definition.
(I have seen 'Terrible temper' mean 'rage' so perhaps 'temper' could also mean 'rage')

'undercover agent's hidden' is the wordplay.
'hidden' indicates the answer is hidden within the clue.
'RAGE' is hidden in the letters of 'undercover agents'.

(Other definitions for rage that I've seen before include "Be furious" , "Extreme anger" , "High dudgeon" , "Latest fashion; high emotion" , "See red" .)

I've seen this clue in The Times.

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