Party, American, owning rage is treacherous (9)
I believe the answer is:
dangerous
'treacherous' is the definition.
(similar in meaning)
'party american owning rage' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'american' becomes 'US' (United States).
'owning' indicates putting letters inside.
'rage' becomes 'anger' (I've seen this in another clue).
'do'+'us'='dous'
'dous' placed around 'anger' is 'DANGEROUS'.
'is' acts as a link.
(Other definitions for dangerous that I've seen before include "menacing" , "Perilous, unsafe" , "Pope: 'A little learning is a . . . . . . . . . thing'" , "Unsafe, risky" , "Posing a hazard" .)