Withdraw from the southeast and give up (6)
I believe the answer is:
secede
'withdraw from' is the definition.
(as in seceding from an organisation)
'southeast and give up' is the wordplay.
'southeast' becomes 'SE' (synonyms).
'and' says to put letters next to each other.
'give up' becomes 'cede' (synonyms).
'se'+'cede'='SECEDE'
'the' is the link.
(Other definitions for secede that I've seen before include "Withdraw formally from membership of an organisation" , "'Withdraw formally, from a political body perhaps (6)'" , "leave union" , "Withdraw from a political federation" , "'Withdraw, break away (6)'" .)