Motet rewritten becomes tribal symbol (5)
I believe the answer is:
totem
'tribal symbol' is the definition.
(I've seen this in another clue)
'motet rewritten' is the wordplay.
'rewritten' is an anagram indicator.
'motet' is an anagram of 'TOTEM'.
'becomes' acts as a link.
(Other definitions for totem that I've seen before include "Pole used in ritual" , "family emblem" , "Symbolic pole" , "Natural item of spiritual significance" , "Natural emblem of spiritual significance" .)