If you describe someone as the standard bearer of a group, you mean that they act as the leader or public representative of a group of people who have the same aims or interests.
She was the standard-bearer for the causes of many African-Americans.
standard-bearer in British English
noun
1.
an officer or person who carries a standard
2.
a leader of a cause or party
standard-bearer in American English
(ˈstændərdˌbɛrər)
noun
1.
the person assigned to carry the standard, or flag, of a group, esp. of a military organization
2.
the leader or chief representative of a movement, political party, etc.
Examples of 'standard-bearer' in a sentence
standard-bearer
He is the final standard-bearer of a generation who knew life outside pristine academies.
Times, Sunday Times (2015)
Loftus-Cheek does not just play as a young man trying to make a career at a big club but the standard-bearer for a generation.