Oratorio is ruined if choir modulate (1,5,2,3,4)
I believe the answer is:
a child of our time
'oratorio' is the definition.
(oratorio by Michael Tippett)
'ruined if choir modulate' is the wordplay.
'ruined' indicates an anagram.
'if'+'choir'+'modulate'='ifchoirmodulate'
'ifchoirmodulate' anagrammed gives 'A CHILD OF OUR TIME'.
'is' is the link.
(Other definitions for a child of our time that I've seen before include "Oratorio by Tippett" , "One newly-delivered" .)