Expensive address for partner (4)
I believe the answer is:
dear
This clue is a double definition.
'expensive' is the first definition.
(similar in meaning)
'address for partner' is the second definition.
(I've seen this before)
(Other definitions for dear that I've seen before include "Expensive or loved" , "love" , "Beloved or costly" , "pet > ducks" , "Treasured" .)