Flag's pattern (8)
I believe the answer is:
standard
I believe this clue is a double definition.
'flag's' is the first definition.
(standard is a kind of flag)
'pattern' is the second definition.
(standard is a kind of pattern)
(Other definitions for standard that I've seen before include "Reference point, benchmark" , "Normal - colours" , "Typical, normal" , "Flag - of the usual kind" , "Military flag" .)