Arranged a slot for some vocalists (5)
I believe the answer is:
altos
'some vocalists' is the definition.
(alto is a kind of vocalist)
'arranged a slot' is the wordplay.
'arranged' indicates anagramming the letters.
'a'+'slot'='aslot'
'aslot' anagrammed gives 'ALTOS'.
'for' acts as a link.
(Other definitions for altos that I've seen before include "High male or low female voices" , "Females who sing in the lowest range" , "Singers" , "Choir members" , "Highest male, lowest female, voices" .)