Standard tirade is obviously offensive (8)
I believe the answer is:
flagrant
'obviously offensive' is the definition.
'flagrant' can be an answer for 'offensive' (similar in meaning). I am not sure about the 'obviously' bit.
'standard tirade' is the wordplay.
'standard' becomes 'flag' (I've seen this before).
'tirade' becomes 'rant' (both can mean an angry outburst).
'flag'+'rant'='FLAGRANT'
'is' is the link.
Can you help me to learn more?
(Other definitions for flagrant that I've seen before include "Conspicuous, blatant" , "Blatant, outrageous" , "Unashamed" , "Crying" , "Being shameless" .)