Distinctive mark of an infiltrator (4)

I believe the answer is:

mole

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This clue might be a double definition.

'distinctive mark' is the first definition.
'mole' can be an answer for 'mark' (mark on the skin). I am unsure of the 'distinctive' bit.

'an infiltrator' is the second definition.
(I've seen this before)

'of' acts as a link.

Can you help me to learn more?

(Other definitions for mole that I've seen before include "digger" , "Jetty; animal" , "Skin spot; breakwater" , "Agent; breakwater" , "Counterspy" .)

I've seen this clue in The Irish Independent.

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