One's ecstatic after daughter's protest (7)
I believe the answer is:
dissent
'protest' is the definition.
('dissent' can be a synonym of 'protest')
'one's ecstatic after daughter's' is the wordplay.
'one's' becomes 'is' (roman numeral).
'ecstatic' becomes 'sent' (I've seen this in other clues).
'after' means one lot of letters go next to another.
'daughter' becomes 'd'.
'is'+'sent'='issent'
'issent' after 'd' is 'DISSENT'.
(Other definitions for dissent that I've seen before include "Object" , "Disagree" , "Open disagreement" , "Withhold approval" , "Dispute" .)