Triumph cleric found in bucket (7)
I believe the answer is:
prevail
'triumph' is the definition.
(synonyms)
'cleric found in bucket' is the wordplay.
'cleric' becomes 'Rev' (abbreviation for Reverend).
'found in' means one lot of letters goes inside another.
'bucket' becomes 'pail' (synonyms).
'rev' going inside 'pail' is 'PREVAIL'.
(Other definitions for prevail that I've seen before include "Win through" , "Gain mastery" , "Succeed ultimately" , "Successfully persuade" , "Get one's way" .)