US city linked to Irish haunt (4)
I believe the answer is:
lair
'haunt' is the definition.
(I've seen this in another clue)
'us city linked to irish' is the wordplay.
'us city' becomes 'LA' (Los Angeles).
'linked to' says to put letters next to each other.
'irish' becomes 'IR' (abbreviation for Irish).
'la'+'ir'='LAIR'
(Other definitions for lair that I've seen before include "Flashy man" , "Wild animal's den" , "Rail around animal's den" , "office?" , "Private place of seclusion" .)