Parasite in record dispute sent back millions (8)
I believe the answer is:
tapeworm
'parasite' is the definition.
(I've seen this before)
'record dispute sent back millions' is the wordplay.
'record' becomes 'tape' (taping is a kind of recording).
'dispute' becomes 'row' (row is a kind of dispute).
'sent back' says the letters should be written in reverse.
'millions' becomes 'm' (abbreviation).
'row' in reverse letter order is 'wor'.
'tape'+'wor'+'m'='TAPEWORM'
'in' acts as a link.
(Other definitions for tapeworm that I've seen before include "Internal parasite" , "Ribbon-like parasite inhabiting the gut" , "Sucker" , "Intestinal parasite" , "Human parasite" .)