Stop to find a house in Washington (4)
I believe the answer is:
whoa
'stop' is the definition.
(I've seen this before)
'a house in washington' is the wordplay.
'a house' becomes 'ho' (abbreviation for house).
'in' means one lot of letters goes inside another.
'washington' becomes 'wa'.
'ho' inserted inside 'wa' is 'WHOA'.
'to find' acts as a link.
(Other definitions for whoa that I've seen before include "Said to stop a horse" , "Hold your horses!" , "halt" , "Call to stop" , "Stop! - steady on!" .)