Sneaky on a regular basis? No! (3)
I believe the answer is:
nay
'no' is the definition.
(I've seen this before)
'sneaky on a regular basis?' is the wordplay.
'on a regular basis?' means one should take alternating letters.
The alternating letters of 'sneaky' are 'NAY'.
(Other definitions for nay that I've seen before include "telling a nicker from a pony?" , "even" , "Negative answer" , "Refusal" , "Denial" .)