Mite - different thing (4)
I believe the answer is:
item
'thing' is the definition.
(an item is a thing)
'mite different' is the wordplay.
'different' indicates anagramming the letters (letters placed in a different order).
'mite' anagrammed gives 'ITEM'.
(Other definitions for item that I've seen before include "Article (on list or in news)" , "Record" , "Part of a list" , "One thing on a list" , "Piece in paper" .)