Mad King visiting US siege city (5)
I believe the answer is:
wacko
'mad' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for wacko that I've seen before include "demented creature" , "Out to lunch" , "Nutter" , "Mad" , "nuts" .)