To do urgently -- masking smell (5)

I believe the answer is:

odour

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'smell' is the definition.
(synonyms)

'to do urgently masking' is the wordplay.
'ODOUR' is hidden within the letters.
But, I'm unsure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for odour that I've seen before include "pervasive quality" , "Any property detected by the olfactory system" , "reputation" , "Whiff" , "Aroma or fragrance" .)

I've seen this clue in The Telegraph.

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