English rock band, once big in the East? (4)
I believe the answer is:
asia
This clue is a double definition.
'english rock band once big' is the first definition.
(Asia were an English rock band of the 1980s)
'the east?' is the second definition.
(east is a kind of Asia)
'in' acts as a link.
(Other definitions for asia that I've seen before include "Largest land-mass" , "A great deal of land" , "A vast number of people have lived here" , "The nations of the East, collectively" , "One-third of all land" .)