Item packed in a case under black beachwear (7,4)

'beachwear' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I can't see?

'item packed in a case under black' is the wordplay.
'item' becomes 'thing' (I've seen this before).
'packed in' means one lot of letters goes inside another.
'case' becomes 'suit' (synonyms).
'under' says to put letters next to each other.
'black' becomes 'b' (as in pencil classifications).
'a'+'suit'='asuit'
'thing' going inside 'asuit' is 'athingsuit'.
'athingsuit' after 'b' is 'BATHING SUIT'.

Can you help me to learn more?