Mysterious beggar can enter houses (6)
I believe the answer is:
arcane
'mysterious' is the definition.
(I've seen this in another clue)
'beggar can enter houses' is the wordplay.
'houses' says the answer is hidden in the clue (part of the clue houses the answer).
'ARCANE' is hidden in the letters of 'beggar can enter'.
(Other definitions for arcane that I've seen before include "Recondite" , "Mysterious, understood by few" , "Requiring special knowledge" , "Requiring secret or mysterious knowledge" , "deep" .)