Definitely not the very smallest (5,2,3)

'definitely' is the definition.
Both the answer and definition are adverbs. Maybe they are linked in a way I don't understand?

'the very smallest' is the wordplay.
I cannot really see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
'very' could be 'so' (both can mean 'extremely') and 'so' is located in the remaining letters.
This may be the basis of the clue (or it may be nonsense).

'not' is the link.

Can you help me to learn more?