Hairy bug found in party by American (9)
I believe the answer is:
dangerous
'hairy' is the definition.
(thesaurus)
'bug found in party by american' is the wordplay.
'bug' becomes 'anger' (**).
'found in' means one lot of letters goes inside another.
'party' becomes 'do' (do is a kind of party).
'by' is a charade indicator (letters next to each other).
'american' becomes 'us'.
'anger' put inside 'do' is 'dangero'.
'dangero'+'us'='DANGEROUS'
(Other definitions for dangerous that I've seen before include "Perilous, unsafe" , "Hairy" , "Insecure" , "likely to blow up" , "Hazardous" .)