Where Cain, in his wandering, came to a valley (8)
I believe the answer is:
valencia
'his wandering came to a valley' is the definition.
The definition suggests a singular noun which matches the answer.
'where cain' is the wordplay.
I cannot really understand how this works, but
an anagram of 'cain' is 'ncia' which is within the answer.
The remaining letters 'vale' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'in' is the link.
Can you help me to learn more?
(Other definitions for valencia that I've seen before include "Spanish city and region" , "European city" , "Region and major port of eastern Spain" , "Spanish port" , "port in the Med" .)