Each way but in only one direction (4)
I believe the answer is:
east
'in only one direction' is the definition.
'east' can be an answer for 'direction' (compass direction). I am unsure of the 'in only one' bit.
'each way' is the wordplay.
'each' becomes 'ea' (abbreviation).
'way' becomes 'st' (abbreviation for street).
'ea'+'st'='EAST'
'but' acts as a link.
Can you help me to learn more?
(Other definitions for east that I've seen before include "Direction taken when going from the US towards Ireland" , "Opposite of west" , "Sunrise direction" , "Asia" , "Player in deal" .)