Old costume a male one in Japanese art (7)
I believe the answer is:
origami
'japanese art' is the definition.
(I've seen this before)
'old costume a male one' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'costume' becomes 'rig' (I've seen this in other clues).
'male' becomes 'm' (common abbreviation).
'one' becomes 'I' (Roman numeral).
'o'+'rig'+'a'+'m'+'i'='ORIGAMI'
'in' acts as a link.
(Other definitions for origami that I've seen before include "It's crafty folding" , "folding stuff?" , "The folding of sheets" , "Eastern art" , "Art originally created in simple materials to design bird forms" .)