Spot spy, one hiding underground (4)

I believe the answer is:

mole

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This might be a double definition.

'spot' is the first definition.
(spot or blemish on the skin)

'spy one hiding underground' is the second definition.
'mole' can be an answer for 'spy' (I've seen this in another clue). I am unsure of the 'one hiding underground' bit.

Can you help me to learn more?

(Other definitions for mole that I've seen before include "Furry burrowing animal" , "Small congenital skin spot" , "Jetty; animal" , "Skin spot; breakwater" , "Groyne" .)

I've seen this clue in The Irish Times.

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