Foreign Office meets odd discussion group (5)
I believe the answer is:
forum
'discussion group' is the definition.
(I've seen this before)
'foreign office meets odd' is the wordplay.
'foreign office' becomes 'FO' (abbreviation).
'meets' means one lot of letters go next to another.
'odd' becomes 'rum' (rum can mean strange or dubious).
'fo'+'rum'='FORUM'
(Other definitions for forum that I've seen before include "Place for open discussion" , "Tribunal" , "Arena for debate" , "Roman meeting place" , "Place where public meeting or discussion is held" .)