Confiscate one million quid (7)
I believe the answer is:
impound
'confiscate' is the definition.
('impound' can be a synonym of 'confiscate')
'one million quid' is the wordplay.
'one million' becomes 'im' (I've seen this in other clues).
'quid' becomes 'pound' ('pound' can be a synonym of 'quid').
'im'+'pound'='IMPOUND'
(Other definitions for impound that I've seen before include "Seize and take into legal custody" , "Take property into legal custody" , "Shut up" , "Confiscate" , "Seize and confine (illegal vehicle)" .)