Men must vacate rank Portaloo (7)
I believe the answer is:
commode
'must vacate rank portaloo' is the definition.
I can't judge whether this definition defines the answer.
'men' is the wordplay.
I cannot quite understand how this works, but
'men' could be 'mm' (N is short for knight - man can mean a chess piece) and 'mm' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for commode that I've seen before include "Chair containing chamber pot" , "Keeper of a potty" , "Chest of drawers" .)