How a spy is an asset (4)

I believe the answer is:

pays

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'is an asset' is the definition.
I can't tell whether this defines the answer.

'how a spy' is the wordplay.
'how' indicates anagramming the letters (I've seen this in other clues).
'a'+'spy'='aspy'
'aspy' with letters rearranged gives 'PAYS'.

Can you help me to learn more?

(Other definitions for pays that I've seen before include "Foots the bill" , "Remunerates" , "Coughs up" , "Is profitable, country (Fr.)" , "(13) [FRENCH] Country" .)

I've seen this clue in the Evening Standard.

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