Infiltrators
'infiltrators' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for moles that I've seen before include "Small velvety-furred burrowing mammals" , "Breakwaters" , "Small dark spots on the skin" , "Velvety burrowing mammals" , "Skin spots or burrowing animals" .)
'infiltrators' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for spies that I've seen before include "Secret agents" , "Undercover agents" , "Eg, CIA" , "Double agents" , "Snoops" .)