Oddly, cantata is half satire - that costume, for example! (6)
I believe the answer is:
attire
'that costume for example' is the definition.
(costume is a kind of attire)
'oddly cantata is half satire' is the wordplay.
'oddly' means one should take alternating letters (letters in the odd-numbered positions are used).
'is half' indicates taking half.
The alternate letters of 'cantata' are 'att'.
'satire' cut in half is 'ire'.
'att'+'ire'='ATTIRE'
(Other definitions for attire that I've seen before include "'Dress, garb (6)'" , "Formal clothes" , "Clothes worn" , "Garments" , "Clothing, apparel" .)