Vilify a number of Romans breaking ceasefire (7)
I believe the answer is:
traduce
'vilify' is the definition.
(I've seen this in another clue)
'a number of romans breaking ceasefire' is the wordplay.
'a number of romans' becomes 'ad' (I can't justify this - if you can you should give a lot more credence to this answer).
'breaking' is an insertion indicator.
'ceasefire' becomes 'truce' (both can mean a break in fighting).
'ad' put within 'truce' is 'TRADUCE'.
Can you help me to learn more?
(Other definitions for traduce that I've seen before include "Calumniate" , "Malign -- rude act (anag)" , "Defame, slander" , "'Malign, badmouth (7)'" , "Speak ill of" .)