Gunners side taking international trophy borders on strangeness (6)
I believe the answer is:
rarity
'strangeness' is the definition.
'gunners side taking international trophy borders' is the wordplay.
'gunners' becomes 'ra' (Royal Artillery).
'side' becomes 'r' (abbreviation for right**).
'taking' is a charade indicator (letters next to each other).
'international' becomes 'i' (abbreviation eg in IMF).
'borders' means to remove the middle letters (only the edge or border letters remain).
'trophy' with its middle taken out is 'ty'.
'ra'+'r'+'i'+'ty'='RARITY'
'on' is the link.
(Other definitions for rarity that I've seen before include "something quite unusual" , "Something very scarce and often valuable" , "Something unusual, perhaps collectible" , "Something uncommon" , "Uncommon object" .)