The Lord will save old Queen singer (9)
I believe the answer is:
chorister
'singer' is the definition.
(singer in a choir)
'the lord will save old queen' is the wordplay.
'the lord' becomes 'christ' (Christ is an example).
'will save' means one lot of letters goes inside another (inserted letters are held or saved).
'old' becomes 'o' (abbreviation).
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'christ' placed around 'o' is 'chorist'.
'chorist'+'er'='CHORISTER'
(Other definitions for chorister that I've seen before include "Boy in church" , "Church, cathedral singer" , "Boy singing" , "Boy singer" , "Choirboy or girl" .)