Prussian and Roman thus endure (7)
I believe the answer is:
undergo
'endure' is the definition.
(I know that endure is a more specific form of experience)
'prussian and roman thus' is the wordplay.
I cannot really understand how this works, but
'and' could be 'n' (common abbreviation for 'and') and 'n' is found in the answer.
'thus' could be 'ergo' (I've seen this before) and 'ergo' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for undergo that I've seen before include "Experience or live through" , "Suffer reverse" , "put up with" , "Endure - urged on (anag)" , "Guerdon (anag.)" .)