Singer in Turandot lapped up (4)
I believe the answer is:
alto
'singer' is the definition.
(type of singing voice)
'in turandot lapped up' is the wordplay.
'in' indicates the answer is hidden within the clue.
'up' is a reversal indicator (in down clue: letters go upwards).
'otla' is hidden within 'turandot lapped'.
'otla' written backwards gives 'ALTO'.
(Other definitions for alto that I've seen before include "Kind of singing voice, male or female" , "Key old > male who scores high" , "Highest male voice: lowest female voice" , "Singing range" , "Low female singing voice" .)