Not all like this with yours truly (4)
I believe the answer is:
some
'not all' is the definition.
(I know this)
'like this with yours truly' is the wordplay.
'like this' becomes 'so' ('like so').
'with' is a charade indicator (letters next to each other).
'yours truly' becomes 'me' (the person who set this crossword).
'so'+'me'='SOME'
(Other definitions for some that I've seen before include "Hard work" , "A little; not a little" , "certain" , "Several" , "An unspecified quantity, not all" .)