Left it in care of former editor (6)
I believe the answer is:
exited
'left' is the definition.
('exit' can be a synonym of 'leave')
'it in care of former editor' is the wordplay.
I cannot really see how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is located in the answer.
'former' could be 'ex' (prefix meaning former or onetime) and 'ex' is present in the answer.
'editor' could be 'ed' and 'ed' is found within the answer.
A single letter 'i' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for exited that I've seen before include "Went out, probably through door" , "Took one's leave" , "Went out as actors do" , "Left the stage" , "Went out, departed" .)