Leave out an order for it (4)
I believe the answer is:
omit
'leave out' is the definition.
(I know that leave out can be written as omit)
'an order for it' is the wordplay.
'an order' becomes 'om' (Order of Merit).
'for' says to put letters next to each other.
'om'+'it'='OMIT'
(Other definitions for omit that I've seen before include "Fail (to do something)" , "Leave out or forget" , "Leave out, perhaps in error" , "Exclude; veto" , "Skip" .)