A land we reunited in Anglo-Saxon England (7)
I believe the answer is:
danelaw
'anglo-saxon england' is the definition.
The definition suggests a singular noun which matches the answer.
'a land we reunited' is the wordplay.
'reunited' indicates an anagram (I've seen 'reuniting' mean this (letters are put together again in a new way)).
'a'+'land'+'we'='alandwe'
'alandwe' with letters rearranged gives 'DANELAW'.
'in' is the link.
Can you help me to learn more?
(Other definitions for danelaw that I've seen before include "Viking-occupied England" , "Part of country once" , "NE England, once" , "old north" , "Northern part of England when under foreign rule" .)