Scene and dubious claim about us — it creates mood (10,5)
I believe the answer is:
incidental music
'it creates mood' is the definition.
The definition suggests a singular noun which matches the answer.
'scene and dubious claim about us' is the wordplay.
'scene' becomes 'incident' (I can't justify this - if you can you should give a lot more credence to this answer).
'and' is a charade indicator (letters next to each other).
'dubious' indicates an anagram.
'about' indicates putting letters inside.
'claim' is an anagram of 'almic'.
'almic' going around 'us' is 'almusic'.
'incident'+'almusic'='INCIDENTAL MUSIC'
Can you help me to learn more?
(Other definitions for incidental music that I've seen before include "Notes on film" , "that creates a mood" , "Background to a film or play" .)