Denounce Conservative study swallowing millions (7)
I believe the answer is:
condemn
'denounce' is the definition.
(I know that condemn is a more specific form of the action denounce)
'conservative study swallowing millions' is the wordplay.
'conservative' becomes 'con' (abbreviation for Conservative).
'study' becomes 'den' (term for a study or office).
'swallowing' indicates putting letters inside.
'millions' becomes 'm' (abbreviation).
'den' enclosing 'm' is 'demn'.
'con'+'demn'='CONDEMN'
(Other definitions for condemn that I've seen before include "Denounce" , "To doom" , "Express strong disapproval of" , "Reprove" , "Censure" .)