Discredit

10 clues
Defame
Impugn
Disgrace.
Prove false
Cast doubt on
Refuse to believe
Drag through the mud
Damage reputation of
Show to be untrustworthy
Damage the reputation of
Similar answers:
Academiccredit
Accredit
Accreditation
Accredited
Accredits
Adiscussion
Afulldisclosure
Ageofdiscovery
Apcredit
Appleofdiscord
Asdiscussed
Atadiscount
Availablecredit
Avoiddiscussing
Badcredit
Bankcredit
Bareditall
Bayhoncredit
Beoutdisced
Blooddiscount