Singer up in Scotland (4)
I believe the answer is:
alto
'singer' is the definition.
(alto is a kind of singer)
'up in scotland' is the wordplay.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'in' indicates a hidden word.
'otla' can be found hidden inside 'scotland'.
'otla' back-to-front is 'ALTO'.
(Other definitions for alto that I've seen before include "Second of four parts (in singing)" , "One who sings" , "Counter-tenor or contralto" , "Unisex vocal range" , "Singing range" .)