Untrusting (5)
'untrusting' is the definition.
(synonyms)
This is all the clue.
(Other definitions for leery that I've seen before include "Knowing" , "Shy" , "Sly, cunning" , "Cautious due to suspicions" , "Suspiciously cautious" .)
(Other definitions for sceptical that I've seen before include "Disinclined to believe" , "dubious" , "Inclined not to believe" , "Inclined to doubt accepted opinions" , "Inclined to disbelieve, not convinced" .)