Demanding deep thought, expert discovered (8)

I believe the answer is:

profound

'demanding deep thought' is the definition.

'expert discovered' is the wordplay.
'expert' becomes 'pro' (I've seen this before).
'discovered' becomes 'found' (finding is a kind of discovering).
'pro'+'found'='PROFOUND'

(Other definitions for profound that I've seen before include "anything but superficial" , "deeply intellectual" , "Needing deep thought" , "showing great knowledge" , "Overpowering" .)

I've seen this clue in The Times.

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