Chocolate snack time? Not so, with respect to meals! (5)
I believe the answer is:
twixt
'not so with respect to meals' is the definition.
I can't tell whether this defines the answer.
'chocolate snack time?' is the wordplay.
'chocolate snack' becomes 'Twix' (Twix is a chocolate brand).
'time?' becomes 't' (abbreviation).
'twix'+'t'='TWIXT'
(Other definitions for twixt that I've seen before include "Between (archaic)" , "dividing" .)