Band leader in Scotland, a pipe down (4)
I believe the answer is:
sash
'band' is the definition.
(a band of material)
'leader in scotland a pipe down' is the wordplay.
'leader in' suggests taking the first letters.
'pipe down' becomes 'sh' (I've seen this in other clues).
The first letter of 'scotland' is 's'.
's'+'a'+'sh'='SASH'
(Other definitions for sash that I've seen before include "Window frame - shoulder band" , "Framework holding window panes" , "Band of cloth" , "Brown bread for waist or shoulder" , "Decorative band" .)