Some bathing suits are flimsy (4)
I believe the answer is:
thin
'flimsy' is the definition.
(I know that flimsy can be written as thin)
'some bathing suits' is the wordplay.
'some' indicates the answer is hidden within the clue (some parts of the word are used).
'THIN' is hidden within 'bathing suits'.
'are' is the link.
(Other definitions for thin that I've seen before include "as 7 [LOAF] may be sliced" , "Implausible" , "Lean; make (plants) less crowded" , "Dilute; lean" , "Lacking substance; not dense" .)