Do all these songs sound like number one? (6)
I believe the answer is:
lieder
'do all these songs sound like number' is the definition.
The definition suggests an adverb but the answer is not.
'one?' is the wordplay.
I cannot really understand how this works, but
'one?' could be 'li' (I've seen this in other clues) and 'li' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for lieder that I've seen before include "songs by Schumann?" , "Relied on classical German song" , "Relied on German song (6)." , "songs from Berlin?" , "Relied on German song genre" .)