Disloyal to America without justification (10)
I believe the answer is:
treasonous
'disloyal' is the definition.
('treasonous' can be similar in meaning to 'disloyal')
'to america without justification' is the wordplay.
'america' becomes 'us' (abbreviation for the United States).
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'justification' becomes 'reason' (I've seen this before**).
'to'+'us'='tous'
'tous' placed around 'reason' is 'TREASONOUS'.
(Other definitions for treasonous that I've seen before include "Like Benedict Arnold, for some!" , "subversive" , "disloyal" , "liable to harm the homeland" , "Betraying one's country" .)