Painter in red? (6)
I believe the answer is:
titian
I believe this clue is a double definition.
'painter' is the first definition.
(I know that Titian is a old master)
'red?' is the second definition.
(I know that titian is a type of red)
'in' is the link.
(Other definitions for titian that I've seen before include "Italian painter; hair colour" , "It. painter, famous for redheads" , "Italian painter of the Venetian school, patronised by Philip II of Spain" , "painting" , "Sixteenth cenntury Italian painter" .)