Throwaway lines from The Undertones on stage
I believe the answer is:
asides
'the undertones on stage' is the definition.
(I've seen this before)
'throwaway lines' is the wordplay.
'throwaway' becomes 'a' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'lines' becomes 'sides' (side is a kind of line).
'a'+'sides'='ASIDES'
'from' acts as a link.
Can you help me to learn more?
(Other definitions for asides that I've seen before include "Daises (anag.)" , "Players aren't meant to hear these" , "not everyone hears them" , "Incidental remarks" , "confidences passed on to spectators by players" .)