Coin found under a Catholic's grave? (6)
I believe the answer is:
accent
'grave?' is the definition.
(grave is a kind of accent)
'coin found under a catholic's' is the wordplay.
'coin' becomes 'cent' (cent is a kind of coin).
'found under' means one lot of letters go next to another.
'catholic' becomes 'C' (abbreviation as in RC for Roman Catholic).
'a'+'c'='ac'
'cent' after 'ac' is 'ACCENT'.
(Other definitions for accent that I've seen before include "Possibly a grave sign" , "Acute, perhaps" , "Distinctive local way of speaking" , "Mark used to indecate pronunciation" , "Grave, perhaps" .)