Bring up obsessive to understand (4)

I believe the answer is:

know

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

'understand' is the definition.
(I've seen this in another clue)

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for know that I've seen before include "Be dangerously well informed" , "Articulated" , "Recognise" , "Ken" , "Have information" .)

I've seen this clue in The Independent.

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