Sad Scottish singer half-cut in empty brasserie (4)
I believe the answer is:
blue
'sad' is the definition.
(I know that sad can be written as blue)
'scottish singer half-cut in empty brasserie' is the wordplay.
'scottish singer' becomes 'Lulu'.
'half cut' indicates taking half.
'in' means one lot of letters goes inside another.
'empty' says to hollow out the word (remove centre letters).
'brasserie' with its middle taken out is 'be'.
'lulu' cut in half is 'lu'.
'lu' inserted into 'be' is 'BLUE'.
(Other definitions for blue that I've seen before include "University sportsman - a shade - depressed" , "Conservative > depressed" , "Morose; colour" , "Sea colour" , "Primary colour" .)