Franco-Prussian agreement on board? (5)
I believe the answer is:
ouija
'board?' is the definition.
(I know that Ouija is a type of board)
'franco-prussian agreement on' is the wordplay.
'franco prussian' becomes 'ja' (I can't explain this - if you can you should believe this answer much more).
'agreement' becomes 'oui' ('yes' in French).
'on' says to put letters next to each other.
'ja' after 'oui' is 'OUIJA'.
Can you help me to learn more?
(Other definitions for ouija that I've seen before include "This board is used in spiritualist proceedings" , "Something to raise spirits" , "Board for contacting spirits" , "Occult board" , "Board able to answer questions?" .)