Neglect to order the thing (4)
I believe the answer is:
omit
'neglect' is the definition.
('omit' can be a synonym of 'neglect')
'order the thing' is the wordplay.
'order' becomes 'om' (order of merit).
'the thing' becomes 'it'.
'om'+'it'='OMIT'
'to' acts as a link.
(Other definitions for omit that I've seen before include "Don't include" , "Leave out or undone" , "Leave out or fail to do" , "Exclude - neglect" , "Leave something out" .)