Standard in decline (4)
I believe the answer is:
flag
I believe this clue is a double definition.
'standard' is the first definition.
(thesaurus)
'decline' is the second definition.
(thesaurus)
'in' is the link.
(Other definitions for flag that I've seen before include "appears to grow languid" , "part of pavement" , "Get weary" , "Mark for attention" , "fade" .)