Real gem (6)
(Other definitions for work of art that I've seen before include "Aesthetic product" , "A fine building, picture, book etc - aesthetic labour" , "tour de force?" , "skilful achievement" , "Oil, perhaps" .)
(Other definitions for beaut that I've seen before include "cracker" , "fine thing" , "16 down's fine or attractive example of something" .)
(Other definitions for keeper that I've seen before include "Cain asked 'Am I my brother's ......?'" , "Goal minder" , "One at the wicket" , "Holder; museum official" , "SECOND PART OF 16" .)