... advocate for Eastern partner (7)
I believe the answer is:
espouse
'advocate' is the definition.
(I've seen this in another clue)
'eastern partner' is the wordplay.
'eastern' becomes 'e'.
'partner' becomes 'spouse' (synonyms).
'e'+'spouse'='ESPOUSE'
'for' acts as a link.
(Other definitions for espouse that I've seen before include "Give support to - see soup (anag)" , "See opus (anag)" , "Give support to, say a cause" , "Take in marriage" , "See opus to support a cause" .)