Dull Soviet spy (5)
I believe the answer is:
blunt
I believe this clue is a double definition.
'dull' is the first definition.
(synonyms)
'soviet spy' is the second definition.
(I've seen this before)
(Other definitions for blunt that I've seen before include "Candid" , "To the point; without point" , "Straightforward" , "not cutting" , "Take the edge off" .)