Band's mega hit Motown initially put out (4)
I believe the answer is:
sash
'band's' is the definition.
(sash is a kind of band)
I don't understand how the remainder of the clue works.
(Other definitions for sash that I've seen before include "Window frame - shoulder band" , "seen hanging around Miss World?" , "Strip of cloth - type of window" , "Decorative belt" , "Brown bread for waist or shoulder" .)