Double agents (5)

I believe the answer is:
moles
'double agents' is the definition.
('mole' can be a synonym of 'double agent')
This is the entire clue.
(Other definitions for moles that I've seen before include "Velvety burrowing mammals" , "Breakwaters" , "Small velvety-furred burrowing mammals" , "Burrowing animals or small growths on skin" , "Traitorous spies" .)