Build up a band on the radio (6)
I believe the answer is:
accrue
'build up' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for accrue that I've seen before include "Collect" , "what interest payments do" , "Fall due; accumulate" , "mount up" , "Accumulate or grow like interest" .)