Parson reformed old singer (7)
I believe the answer is:
soprano
'singer' is the definition.
(type of singing voice)
'parson reformed old' is the wordplay.
'reformed' indicates an anagram.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'parson' anagrammed gives 'sopran'.
'sopran'+'o'='SOPRANO'
(Other definitions for soprano that I've seen before include "High singing voice" , "Sutherland?" , "Norman, perhaps" , "Female singer" , "chorus girl, perhaps" .)