Untrustworthy sort
I believe the answer is:
sneak
'untrustworthy sort' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sneak that I've seen before include "Tale-teller; go furtively" , "Move furtively - tell tales" , "Creep" , "thief" , "Prowl" .)