Playfully, 'pieces of eight'? (6)
I believe the answer is:
octets
'eight'?' is the definition.
('octet' can be a synonym of 'eight')
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for octets that I've seen before include "Groups of eight peformers" , "Groups of eight, often singers" , "groups of eight, say singers" , "Sets of eight" .)