One million flowers - these may enhance front - or rear! (8)
I believe the answer is:
implants
'enhance front or rear' is the definition.
I can't judge whether this defines the answer.
'one million flowers these may' is the wordplay.
'one million' becomes 'im' (resembles pm).
'flowers these may' becomes 'plants' (I can't explain this - if you can you should give a lot more credence to this answer).
'im'+'plants'='IMPLANTS'
Can you help me to learn more?
(Other definitions for implants that I've seen before include "grafts" , "Inserts, ideas in mind or substance into living tissue" , "bust up thanks to these" .)