Going astray dooms wicked old city (5)
I believe the answer is:
sodom
'wicked old city' is the definition.
'sodom' can be an answer for 'city' (cities of the plain from Genesis). I'm not certain of the 'wicked old' bit.
'going astray dooms' is the wordplay.
'going astray' indicates anagramming the letters.
'dooms' with letters rearranged gives 'SODOM'.
Can you help me to learn more?
(Other definitions for sodom that I've seen before include "Wicked Biblical city, twinned with Gomorrah" , "One of the Old Testament cities destroyed for its wickedness" , "Sinful city of the Bible" , "place of utter depravity" , "Depraved town (Bible)" .)