Parnassian location's key character there (6)
I believe the answer is:
delphi
'parnassian location's' is the definition.
(location on Mount Parnassus)
'key character there' is the wordplay.
'key' becomes 'del' (del key on a keyboard).
'character there' becomes 'phi' (phi is a kind of character. I am not sure about the 'there' bit.).
'del'+'phi'='DELPHI'
(Other definitions for delphi that I've seen before include "Home of the oracle on the slopes of Mount Parnassus" , "Dead ringer" , "Site of classical Greek oracle" , "Ancient Greek city, site of famous oracle" , "Temple site on Mt Parnassus" .)