Possibly able to sound full of menace (7)
I believe the answer is:
baleful
'sound full of menace' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'possibly able to' is the wordplay.
'possibly' is an anagram indicator.
'to' becomes 'ful' (I can't justify this - if you can you should believe this answer much more).
'able' with letters rearranged gives 'bale'.
'bale'+'ful'='BALEFUL'
Can you help me to learn more?
(Other definitions for baleful that I've seen before include "Of evil influence" , "Threatening or foreshadowing evil" , "Of look, menacing or destructive" , "threatening appearance?" , "Menacing - dejected" .)