Suddenly got nasty with a small number (6,2)
I believe the answer is:
turned on
'suddenly got nasty with' is the definition.
(to turn on is to suddenly turn against)
'a small number' is the wordplay.
I cannot quite see how this works, but
'number' could be 'turn' (synonyms) and 'turn' is present in the answer.
This explanation may well be incorrect...
(Other definitions for turned on that I've seen before include "Stimulated" , "Suddenly attacked - state of ecstasy - high" , "Activated - aroused" , "Excited" , "Feeling great excitement" .)