Pennant (4)
'pennant' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for flag that I've seen before include "Iris; ensign" , "Rectangular piece of fabric used as a signalling device" , "Standard; tire" , "Become limp" , "Iris - paving slab" .)
(Other definitions for race that I've seen before include "Care about contest" , "Speed competition" , "Contest; nation" , "Breed" , "People; run" .)