Forget to order the thing? (4)
I believe the answer is:
omit
'forget' is the definition.
(thesaurus)
'order the thing?' is the wordplay.
'order' becomes 'om' (order of merit).
'the thing?' becomes 'it'.
'om'+'it'='OMIT'
'to' is the link.
(Other definitions for omit that I've seen before include "Leave out or fail to do" , "Drop" , "Don't include" , "Disregard" , "Fail to mention" .)