She’s beautiful, but can sound alarming (5)
I believe the answer is:
belle
'she's' is the definition.
'sound alarming' is the wordplay.
'sound' becomes 'bell' (bell is a kind of sound).
'alarming' becomes 'e' (I am not sure about this - if you are sure you should believe this answer much more).
'bell'+'e'='BELLE'
'beautiful but can' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for belle that I've seen before include "Reigning beauty" , "Attractive woman" , "Beautiful woman - of the ball?" , "dish" , "Pretty girl" .)