Singers in a special Tosca production (5)
I believe the answer is:
altos
'singers' is the definition.
(alto is a kind of singer)
'in a special tosca production' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ALTOS' is hidden in the letters of 'special tosca production'.
(Other definitions for altos that I've seen before include "Highest male, lowest female, voices" , "Lowest female singing voices" , "High male or low female voices" , "Choir members" , "Females who sing in the lowest range" .)