Motet composed as a sort of family emblem (5)
I believe the answer is:
totem
'family emblem' is the definition.
(I've seen this in another clue)
'motet composed' is the wordplay.
'composed' indicates anagramming the letters.
'motet' with letters rearranged gives 'TOTEM'.
'as a sort of' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for totem that I've seen before include "Symbolic object with ritualistic associations" , "Pole used in ritual" , "Emblematic animal or object" , "Native American symbol" , "symbol representing clan" .)