So rich a blend of voices (6)
I believe the answer is:
choirs
'voices' is the definition.
Although both the answer and definition are verbs in their -s form, I don't see how they can define each other.
'so rich a blend' is the wordplay.
'a blend' is an anagram indicator (I've seen 'blended' mean this).
'so'+'rich'='sorich'
'sorich' with letters rearranged gives 'CHOIRS'.
'of' is the link.
Can you help me to learn more?
(Other definitions for choirs that I've seen before include "Bands of singers" , "Groups of singers, in church say" , "Groups of singers, often in churches" , "Singing groups" , "Singing teams" .)