Gallery lost half of Caravaggio works (6)
I believe the answer is:
loggia
'gallery' is the definition.
(type of gallery or corridor)
'lost half of caravaggio works' is the wordplay.
'lost' becomes 'l' (abbreviation in sporting league tables).
'half of' indicates taking half.
'works' is an anagram indicator (work can mean to twist or convulse).
'caravaggio' cut in half is 'aggio'.
'aggio' is an anagram of 'oggia'.
'l'+'oggia'='LOGGIA'
(Other definitions for loggia that I've seen before include "Covered area beside building" , "Covered arcaded gallery" , "Open-sided gallery or arcade" , "Roofed arcade or gallery" , "Open-sided gallery for viewing" .)