Parson surprisingly accompanying old singer (7)
I believe the answer is:
soprano
'singer' is the definition.
(soprano is a kind of singer)
'parson surprisingly accompanying old' is the wordplay.
'surprisingly' is an anagram indicator.
'accompanying' says to put letters next to each other.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'parson' is an anagram of 'sopran'.
'sopran'+'o'='SOPRANO'
(Other definitions for soprano that I've seen before include "Singer who aims high" , "High female voice" , "Highly vocal musician" , "chorus girl, perhaps" , "Producer of high-pitched sounds" .)