Expedition into urban houses (4)
I believe the answer is:
tour
'expedition' is the definition.
(thesaurus)
'into urban houses' is the wordplay.
'houses' indicates the answer is hidden within the clue (part of the clue houses the answer).
'TOUR' can be found hidden inside 'into urban'.
(Other definitions for tour that I've seen before include "A trip round" , "Rout on excursion" , "Spell of military duty" , "Trip visiting several places" , "Drive" .)