Rendered invalid, I'd suffered with Nile flu (9)
I believe the answer is:
nullified
'rendered invalid' is the definition.
The definition and answer can be both related to change as well as being past participle verbs.
Maybe there's a link between them I don't understand?
'i'd suffered with nile flu' is the wordplay.
'suffered with' is an anagram indicator (I've seen 'suffers' mean this).
'nile'+'flu'='nileflu'
'id' mixed up with 'nileflu' makes 'NULLIFIED'.
Can you help me to learn more?
(Other definitions for nullified that I've seen before include "revoked" , "Abrogated" , "Made invalid" , "Scrubbed" , "Cancelled out" .)