Location of diamonds in a deck (7)
I believe the answer is:
address
'location' is the definition.
(address is a kind of location)
'diamonds in a deck' is the wordplay.
'diamonds' becomes 'd' (abbreviation in bridge say).
'in' means one lot of letters goes inside another.
'deck' becomes 'dress' (I've seen this before).
'a'+'dress'='adress'
'd' placed within 'adress' is 'ADDRESS'.
'of' is the link.
(Other definitions for address that I've seen before include "One's designated location" , "Attend" , "hail maybe?" , "directions in window" , "Talk - indication of house" .)