Cave (6)
'cave' is the definition.
(I know that cave can be written as grotto)
This is the entire clue.
(Other definitions for grotto that I've seen before include "Small cave as at Lourdes" , "It's left on Dec 24 by Santa and his reindeer" , "Pretty cave" , "(Imitation) cave" , "A picturesque cave as in Lourdes (6)" .)
(Other definitions for cavern that I've seen before include "Vast dark space" , "Large cave" , "Detection device" , "Grotto" , "Large dark hole in the ground" .)
(Other definitions for art that I've seen before include "The works of Alma-Tadema" , "Trickery" , "Eg, paintings, sculpture" , "eg Painting" , "Works in a gallery" .)
(Other definitions for man that I've seen before include "Bloke" , "Board token; husband" , "Adult human male" , "Dude" , "just one" .)