Devious way to avoid overcrowding in cities (6)
I believe the answer is:
bypass
'devious way' is the definition.
'bypass' can be an answer for 'way' (bypass is a kind of way). I am not sure about the 'devious' bit.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for bypass that I've seen before include "heart operation" , "Way to avoid town etc" , "Sort of surgery" , "Go round (congested area etc)" , "Ring road" .)