It's all over a statement of the obvious about pronoun (5,4)
I believe the answer is:
thats that
'it's all over a statement of the obvious' is the definition.
I know nothing about this answer so I can't tell whether this works.
'about pronoun' is the wordplay.
'about' becomes 'thats' (I can't justify this - if you can you should give a lot more credence to this answer).
'pronoun' becomes 'that' ('that' is a pronoun).
'thats'+'that'='THATS THAT'
Can you help me to learn more?
(Other definitions for thats that that I've seen before include "It's settled and finished; no more about it (4'1,4)" , "one trivially true" , "End of story!" , "Final comment" , "Emphatic conclusion" .)