Pressure on cleric before a Christian observance is common (9)
I believe the answer is:
prevalent
'common' is the definition.
(I've seen this before)
'pressure on cleric before a christian observance' is the wordplay.
'pressure' becomes 'p' (abbreviation).
'on' means one lot of letters go next to another.
'cleric' becomes 'rev' (abbreviation for Reverend).
'before' is a charade indicator (letters next to each other).
'christian observance' becomes 'lent' (Christians observe Lent).
'p'+'rev'+'a'+'lent'='PREVALENT'
'is' is the link.
(Other definitions for prevalent that I've seen before include "Commonplace" , "Ruling" , "Widely accepted" , "general" , "powerful" .)