Angus touchily withholds enthusiasm (5)

I believe the answer is:

gusto

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

'enthusiasm' is the definition.
(gusto is a kind of enthusiasm)

'angus touchily withholds' is the wordplay.
'GUSTO' is hidden in amongst the letters.
But, I'm not sure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for gusto that I've seen before include "Vigorous enthusiasm" , "ardour" , "Great enjoyment in doing something" , "Zest, exuberance" , "(Corporate) emblem" .)

I've seen this clue in The Guardian.

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