### Clue: A warrior – one is a revolutionary besieging ancient city on Sunday (7)
### Answer: SAMURAI 
 ### Explanation: Definition: A warrior
 < { **Reversal of**(revolutionary) [I AM("one is", used to refer to oneself, as in "one is not amused", if one doesn't use the royal "we") + A } **containing**(besieging) UR(a city in biblical times) > **placed after**(on, in an across clue) S(abbrev. for "Sunday").