Poor or richest singer (9)
I believe the answer is:
chorister
'singer' is the definition.
(chorister is a kind of singer)
'poor or richest' is the wordplay.
'poor' is an anagram indicator.
'or'+'richest'='orrichest'
'orrichest' with letters rearranged gives 'CHORISTER'.
(Other definitions for chorister that I've seen before include "Church, cathedral singer" , "Boy singing" , "Boy singer" , "Choirboy or girl" , "Boy in church" .)