Left a section in a document (8)
I believe the answer is:
departed
'left' is the definition.
(departing is a kind of leaving)
'a section in a document' is the wordplay.
'a section' becomes 'part' ('part' can be a synonym of 'section').
'in' is an insertion indicator.
'a document' becomes 'deed' (deed is a kind of document).
'part' going within 'deed' is 'DEPARTED'.
(Other definitions for departed that I've seen before include "Gone, maybe dead" , "Left -- late" , "Dead; set off" , "completely breathless" , "Went - dead" .)