Drink needed after Foreign Office meeting (5)
I believe the answer is:
Here is my best explanation:
'meeting' is the definition.
(forum is a kind of meeting)
'drink needed after foreign office' is the wordplay.
'drink' becomes 'rum' (I've seen this before).
'needed after' says to put letters next to each other.
'foreign office' becomes 'fo'.
'rum' after 'fo' is 'FORUM'.
(Other definitions for forum that I've seen before include "historically square", "Court - conference", "Public meeting place", "Arena for debate", "Ground for discussion", "Where to meet", "Medium for discussion", "old square", "Online message board" and "Tribunal".)