Make improvements to staff editor retains (5)
I believe the answer is:
emend
'make improvements' is the definition.
(I've seen this before)
'staff editor retains' is the wordplay.
'staff' becomes 'men' (I've seen this in other clues).
'editor' becomes 'ed' (abbreviation).
'retains' indicates putting letters inside.
'men' going inside 'ed' is 'EMEND'.
'to' is the link.
(Other definitions for emend that I've seen before include "Edit; make alterations to a draft" , "Correct, revise (text)" , "Remove errors" , "Revise (a text) (E, not A)" , "get rid of faults" .)