This writer's placed with editor assigned (7)
I believe the answer is:
imputed
'assigned' is the definition.
('impute' can be a synonym of 'assign')
'this writer's placed with editor' is the wordplay.
'this writer's' becomes 'im' (the person writing the crossword clues).
'placed' becomes 'put' (I've seen this in other clues).
'with' says to put letters next to each other.
'editor' becomes 'ed'.
'im'+'put'+'ed'='IMPUTED'
(Other definitions for imputed that I've seen before include "Attributed or ascribed, say a fault" , "Attributed (something bad to someone)" .)