In Rome, 50% of divorces had his backing (4)
I believe the answer is:
ovid
'in rome 50% of divorces had his backing' is the definition.
The definition suggests a singular noun which matches the answer.
'had his backing' is the wordplay.
'had' becomes 'd' (in contractions e.g. 'I'd', 'you'd' etc).
'his' becomes 'ivo' (I can't explain this - if you can you should give a lot more credence to this answer).
'backing' says the letters should be written in reverse.
'd'+'ivo'='divo'
'divo' reversed gives 'OVID'.
Can you help me to learn more?
(Other definitions for ovid that I've seen before include "Roman poet, d. about AD17" , "Void for a Latin poet" , "Metamorphoses author" , "Vi, do read the Latin poet" , "Void for old Roman poet" .)