Sometimes includes rejected article (4)
I believe the answer is:
item
'article' is the definition.
(both can mean an object or thing)
'sometimes includes rejected' is the wordplay.
'includes' says the answer is hidden in the clue.
'rejected' says the letters should be written in reverse.
'meti' is hidden in the letters of 'sometimes'.
'meti' back-to-front is 'ITEM'.
(Other definitions for item that I've seen before include "Seperate article in an enumeration" , "point" , "Single unit" , "newspaper article" , "Separate article" .)