Unhappy about housing everyone in US city (6)
I believe the answer is:
dallas
'us city' is the definition.
(I've seen this before)
'unhappy about housing everyone' is the wordplay.
'unhappy' becomes 'sad' (synonyms).
'about' shows that the letters should be reversed in order.
'housing' means one lot of letters goes inside another.
'everyone' becomes 'all' (I've seen this before).
'sad' backwards is 'das'.
'das' enclosing 'all' is 'DALLAS'.
'in' is the link.
(Other definitions for dallas that I've seen before include "US city where JFK was assassinated" , "Texan city and TV series of the 80s" , "oil produced here" , "Mysteriously, all sad in the US city" , "Texas city where JFK was killed" .)