Bit of finery (6)
(Another definition for fallal that I've seen is " Veteran's foppish".)
'bit of finery' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gem that I've seen before include "Diamond, ruby, or emerald" , "perfect specimen" , "Pleasant and cheerful (from German)" , "A precious stone like a diamond or emerald etc" , "Valuable stone" .)