English bishops decline (3)
I believe the answer is:
ebb
'decline' is the definition.
(ebb is a kind of decline)
'english bishops' is the wordplay.
'english' becomes 'e' (abbreviation).
'bishops' becomes 'bb' (I've seen this in other clues).
'e'+'bb'='EBB'
(Other definitions for ebb that I've seen before include "Fall back" , "Flow outwards" , "Tidal retreat" , "recession" , "Receding movement, as of a tide" .)