His ’n’ hers formal wear? No, just his (5,5)

'his n hers' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.

'formal wear? no just his' is the wordplay.
I cannot really understand how this works, but
'formal' could be 'dress' (similar in meaning) and 'dress' is found in the answer.
'wear?' could be 'shirt' (shirt is a kind of wear) and 'shirt' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...