Obvious jingoistic tirade? (8)
I believe the answer is:
flagrant
'obvious' is the definition.
(thesaurus)
'jingoistic tirade?' is the wordplay.
'jingoistic' becomes 'flag' (I can't justify this - if you can you should give a lot more credence to this answer).
'tirade?' becomes 'rant' (both can mean an angry outburst).
'flag'+'rant'='FLAGRANT'
(Other definitions for flagrant that I've seen before include "Of unconcealed outrageousness" , "Crying" , "Patent" , "Barefaced" , "Unashamed" .)