Clergyman is a cutting comedian (8)
I believe the answer is:
chaplain
'clergyman' is the definition.
(I know that Chaplain is a type of clergyman)
'a cutting comedian' is the wordplay.
'cutting' indicates putting letters inside (some letters cut their way into a word).
'comedian' becomes 'Chaplin' (Charlie Chaplin).
'a' inserted within 'chaplin' is 'CHAPLAIN'.
'is' acts as a link.
(Other definitions for chaplain that I've seen before include "'Member of the clergy, in a hospital, say (8)'" , "Clergyman attached to military unit" , "cleric" , "Army padre" , "Clergyman attached to an organisation" .)