Flag is hard to make out (5)
I believe the answer is:
faint
I believe this is a double definition.
'flag' is the first definition.
(thesaurus)
'hard to make out' is the second definition.
(I've seen this in another clue)
'is' acts as a link.
(Other definitions for faint that I've seen before include "Swoon; indistinct" , "woozy" , "hard to hear" , "Barely perceptible" , "dull" .)