For troubled divers, a counsellor (7)

I believe the answer is:

adviser

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

'counsellor' is the definition.
(I've seen this before)

'for troubled divers a' is the wordplay.
'divers a' anagrams to 'ADVISER'.
However, I'm not sure how this is indicated.

Can you help me to learn more?

(Other definitions for adviser that I've seen before include "ID saver (anag.)" , "Guide" , "Counseller" , "subject's specialist consultant" , "Counsellor, mentor" .)

I've seen this clue in The Daily Express.

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