grass roots 
plural noun
1The most basic level of an activity or organization: [as modifier]: improving the game at grass-roots level...
- The Prime Minister said he wanted to create a partnership between Whitehall and individuals and organisations at the grass-roots level.
- Activity in the U.K. and Australia is at the grass-roots level, although some promising movements toward greater public and professional awareness have begun.
- You would not believe the dedication for this company that exists at grass-roots level, and though we are the little people - we ALL make a crucial difference.
1.1Ordinary people regarded as the main body of an organization’s membership: you have lost touch with the grass roots of the party...
- The idea of the rule change was to give greater input to ordinary grass-roots Conservative party members.
- Of the grass-roots membership of the party, a clear majority appears to be on the left.
- A true strategy would take into account many more issues and would be developed with the involvement of grass-roots membership.