Neglect to include (4)
I believe the answer is:
omit
'neglect to include' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for omit that I've seen before include "Disregard" , "Fail to include" , "Leave out or undone" , "Leave out, perhaps in error" , "Leave something out" .)