Discredited official silenced after losing millions (7)
I believe the answer is:
refuted
'discredited' is the definition.
(thesaurus)
'official silenced after losing millions' is the wordplay.
'official' becomes 'ref' (match official in football, say).
'silenced' becomes 'muted' (muting is a kind of silencing).
'after losing' indicates named letters should be taken away.
'millions' becomes 'm' (abbreviation).
'muted' with 'm' taken away is 'uted'.
'ref'+'uted'='REFUTED'
(Other definitions for refuted that I've seen before include "Prove to be false or incorrect" , "Proved (a statement) to be wrong" , "Negated" , "Disproved" , "Denied" .)