Despite the soppy exterior, a person of intelligence (3)

I believe the answer is:

spy

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

'person of intelligence' is the definition.
'spy' can be an answer for 'person' (spy is a kind of person). I'm not sure about the 'of intelligence' bit.

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for spy that I've seen before include "Secret agent of government" , "Keep watch secretly, maybe for foreign government" , "Watch covertly like secret agent" , "One who collects secret information as for government" , "Discover" .)

I've seen this clue in the Evening Standard.

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