Sacrament in Cornish location denied unknown character (7)
I believe the answer is:
penance
'sacrament' is the definition.
(I know that penance is a type of sacrament)
'cornish location denied unknown character' is the wordplay.
'cornish location' becomes 'Penzance' (Penzance is a town in Cornwall).
'denied' is a deletion indicator (the word is denied or deprived of certain letters).
'unknown character' becomes 'z' (algebra).
'penzance' with 'z' taken away is 'PENANCE'.
'in' is the link.
(Other definitions for penance that I've seen before include "act of self-punishment" , "Voluntary punishment to atone for sin" , "Remorse" , "Mortification" , "Self-imposed punishment" .)