Tiny tot swallowing a bit of a snub (6)
I believe the answer is:
minute
'tiny' is the definition.
(minute can mean small)
'tot swallowing a bit of a snub' is the wordplay.
'tot' becomes 'mite' (both can mean a young child).
'swallowing' is an insertion indicator.
'a bit of a snub' becomes 'nu' (I am not sure about this - if you are sure you should believe this answer much more).
'mite' placed around 'nu' is 'MINUTE'.
Can you help me to learn more?
(Other definitions for minute that I've seen before include "Measure of time" , "microscopic" , "Tiny - proportion of time" , "It's not very long" , "Barely perceptible" .)