Boy singer with his rector for excitement (9)
I believe the answer is:
chorister
'boy singer' is the definition.
(I've seen this before)
'with his rector for excitement' is the wordplay.
'with' says to put letters next to each other.
'for excitement' indicates an anagram (I've seen this in other clues).
'his'+'rector' is 'hisrector'.
'hisrector' with letters rearranged gives 'CHORISTER'.
(Other definitions for chorister that I've seen before include "Boy singing" , "Choirboy or girl" , "Boy singer" , "Church, cathedral singer" , "Choir member" .)