Singers getting no rest, unfortunately (6)
I believe the answer is:
tenors
'singers' is the definition.
(tenor is a singing voice)
'getting no rest unfortunately' is the wordplay.
'getting' is an insertion indicator.
'unfortunately' is an anagram indicator (a bad or unfortunate spelling).
'rest' anagrammed gives 'ters'.
'no' inserted within 'ters' is 'TENORS'.
(Other definitions for tenors that I've seen before include "Male singers from Reston" , "Male singers with high register" , "Opera singers" , "Male singing voices" .)