The opposite article is on taxes (10)
I believe the answer is:
antithesis
'the opposite' is the definition.
(I've seen this in another clue)
'article is on taxes' is the wordplay.
'article' becomes 'an' (indefinite article).
'on' is a charade indicator (letters next to each other).
'taxes' becomes 'tithes' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'is' after 'tithes' is 'tithesis'.
'an'+'tithesis'='ANTITHESIS'
Can you help me to learn more?
(Other definitions for antithesis that I've seen before include "opposing view" , "Reverse" , "I oppose the suggestion" , "Opposite; contrasting idea" , "Opposition" .)