In a sneaky way (5)
I believe the answer is:
slyly
'in a sneaky way' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for slyly that I've seen before include "In a stealthy and secret way" , "Craftily, cunningly" , "in underhand way" , "In a cunning manner" .)