No black line in scribbles by copyists
I believe the answer is:
scribes
'copyists' is the definition.
('scribe' can be a synonym of 'copyist')
'no black line in' is the wordplay.
'no black' becomes 'ses' (I am not sure about this - if you are sure you should believe this answer much more).
'line' becomes 'crib' (cribbing is a kind of lining).
'in' indicates putting letters inside.
'ses' going around 'crib' is 'SCRIBES'.
'scribbles by' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for scribes that I've seen before include "People who once made hand-written copies" , "Copyists" , "Ancient writers (7)" , "journos" .)