Priceless work Somalian lost (4,4)
I believe the answer is:
mona lisa
'priceless work' is the definition.
'somalian lost' is the wordplay.
'lost' indicates an anagram.
'somalian' is an anagram of 'MONA LISA'.
(Other definitions for mona lisa that I've seen before include "Leonardo da Vinci's painting of enigmatic woman" , "Mysterious-smile Louvre portrait" , "Leonardo da Vinci's enigmatic portrait" , "Oil" , "Famous painting of enigmatic woman by de Vinci" .)