Motet could become tribal emblem (5)
I believe the answer is:
totem
'tribal emblem' is the definition.
(I've seen this in another clue)
'motet could become' is the wordplay.
'could become' is an anagram indicator.
'motet' anagrammed gives 'TOTEM'.
(Other definitions for totem that I've seen before include "symbolic animal" , "Sign" , "Symbolic pole" , "emblem of tribe?" , "Native American symbol" .)