Sends back rock band with singer to begin with (7)
I believe the answer is:
remands
'sends back' is the definition.
('remand' can be a synonym of 'send back')
'rock band with singer to begin with' is the wordplay.
'rock band' becomes 'rem' (REM are a US rock band).
'with' becomes 'and'.
'to begin with' says to take the initial letters.
The initial letter of 'singer' is 's'.
'rem'+'and'+'s'='REMANDS'
(Other definitions for remands that I've seen before include "Returns prisoner to custody while further evidence is sought" , "Consigns to prison to await trial" , "Returns to custody pending further evidence" , "Sends back" , "Returns prisoner to custody while investigation proceeds" .)