A senator’s organization (4)

I believe the answer is:

nato

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

'organization' is the definition.
(NATO is an example)

'a senator's' is the wordplay.
'NATO' is hidden in amongst the letters.
However, I'm uncertain how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for nato that I've seen before include "Military alliance (acronym)" , "Atlantic alliance (abbr.)" , "Collective security alliance engaged in Bosnia" , "US/Europe alliance" , "Western mil. alliance" .)

I've seen this clue in the Evening Standard.

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