Cancel fine at any time returning stocks (6)
I believe the answer is:
revoke
'cancel' is the definition.
(I know that revoke is a type of cancel)
'fine at any time returning stocks' is the wordplay.
'fine' becomes 'ok' (synonyms).
'at any time' becomes 'ever' (synonyms).
'returning' shows that the letters should be reversed in order.
'stocks' is an insertion indicator.
'ever' backwards is 'reve'.
'ok' placed into 'reve' is 'REVOKE'.
(Other definitions for revoke that I've seen before include "Cancel (a decree, etc)" , "Withdraw or cancel, say a licence" , "Cancel, annul" , "Annul, rescind" , "Withdraw or cancel a decree" .)