One very thin garment reveals all (10)
I believe the answer is:
everything
'all' is the definition.
(all things)
'one very thin garment reveals' is the wordplay.
'reveals' indicates the answer is hidden within the clue.
'EVERYTHING' can be found hidden inside 'one very thin garment'.
(Other definitions for everything that I've seen before include "the works" , "All that is; life in general" , "The whole shebang" , "The whole lot" , "All items" .)