Sullivan is hesitant - covertly disappears (8)

I believe the answer is:

vanishes

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

'disappears' is the definition.
('vanish' can be a synonym of 'disappear')

'sullivan is hesitant covertly' is the wordplay.
'VANISHES' is hidden within the letters.
However, I'm uncertain how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for vanishes that I've seen before include "Becomes invisible" , "Goes quiet" , "Disappears" .)

I've seen this clue in the Sydney Morning Herald.

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