Left section with editor (6)
I believe the answer is:
parted
'left' is the definition.
(parting is a kind of leaving)
'section with editor' is the wordplay.
'section' becomes 'part' (synonyms).
'with' says to put letters next to each other.
'editor' becomes 'ed' (abbreviation).
'part'+'ed'='PARTED'
(Other definitions for parted that I've seen before include "Divided or went separate ways" , "One's hair might be" , "left" , "Divided, broken" , "Divided or separated" .)