FOR my_var IN select distinct some_column from some_table LOOP
  -- do stuff with my_var
END LOOP;

ERROR:  loop variable of loop over rows must be a record
or row variable or list of scalar variables

DECLARE
  somerow RECORD;
  my_var TEXT;
FOR somerow IN select distinct some_column from some_table LOOP
  my_var := somerow.somecolumn;
  -- do stuff with my_var
END LOOP;

DECLARE
  idontcare INT;
  my_var TEXT;
FOR my_var, idontcare IN select distinct some_column, 1 from some_table LOOP
  -- do stuff with my_var
END LOOP;