Singer making a comeback in Scotland (4)
I believe the answer is:
alto
'singer' is the definition.
(alto is a kind of singer)
'a comeback in scotland' is the wordplay.
'a comeback' says the letters should be written backwards.
'in' says the answer is hidden in the clue.
'otla' is hidden within 'scotland'.
'otla' in reverse letter order is 'ALTO'.
'making' acts as a link.
(Other definitions for alto that I've seen before include "Singer's hidden inside chemical toilet" , "Singing voice between tenor and soprano" , "Singing range" , "Woman's singing voice" , "A singing voice or pitch" .)