Hairy sport supporting international organisation (8)
I believe the answer is:
unshaven
'hairy' is the definition.
(thesaurus)
'sport supporting international organisation' is the wordplay.
'sport' becomes 'shaven' (I can't justify this - if you can you should believe this answer much more).
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'international organisation' becomes 'UN' (United Nations).
'shaven' put after 'un' is 'UNSHAVEN'.
(Other definitions for unshaven that I've seen before include "Not having used a razor" , "Stubbly" , "Showing facial stubble" , "Not having removed incipient beard" , "whiskers to deal with?" .)