Prove superior as cleric filling bucket (7)
I believe the answer is:
prevail
'prove superior' is the definition.
(I've seen this before)
'cleric filling bucket' is the wordplay.
'cleric' becomes 'Rev' (abbreviation for Reverend).
'filling' indicates putting letters inside.
'bucket' becomes 'pail' (synonyms).
'rev' placed into 'pail' is 'PREVAIL'.
'as' is the link.
(Other definitions for prevail that I've seen before include "Succeed ultimately" , "get the upper hand" , "Gain mastery" , "Be current" , "Win through" .)