Chaplin runs away with Catholic aboard vessel (7)
I believe the answer is:
chalice
'vessel' is the definition.
(thesaurus)
'chaplin runs away with catholic aboard' is the wordplay.
'chaplin' becomes 'charlie' (Charlie Chaplin).
'runs' becomes 'r' (cricket abbreviation).
'away' indicates named letters should be taken away.
'with catholic' becomes 'c' (abbreviation as in RC for Roman Catholic. I am not sure about the 'with' bit.**).
'aboard' means one lot of letters goes inside another.
'charlie' with 'r' taken away is 'chalie'.
'chalie' enclosing 'c' is 'CHALICE'.
(Other definitions for chalice that I've seen before include "Large goblet for consecrated wine" , "Necessity for communion" , "Wine cup used at Christian Eucharist" , "Cup used in church" , "Church vessel" .)