Guardian search exposes sharks (9)

I believe the answer is:

angelfish

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

'guardian search exposes sharks' is the definition.
I can't tell whether this definition defines the answer.

'guardian search' is the wordplay.
'guardian' becomes 'angel' (I've seen this before).
'search' becomes 'fish' (fishing is a kind of searching).
'angel'+'fish'='ANGELFISH'

Can you help me to learn more?

(Other definitions for angelfish that I've seen before include "Brightly-coloured swimmer" , "shark" .)

I've seen this clue in The Telegraph.

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