Sad teen upset in London region (4,3)
I believe the answer is:
east end
'london region' is the definition.
The definition suggests a singular noun which matches the answer.
'sad teen upset' is the wordplay.
'upset' is an anagram indicator.
'sad'+'teen'='sadteen'
'sadteen' with letters rearranged gives 'EAST END'.
'in' is the link.
Can you help me to learn more?
(Other definitions for east end that I've seen before include "Cockneyland" , "Bow" , "ockney London" , "Cockney's part of London" , "Part of London first to see rising sun" .)