In your code, try enclosing password inside single quote. Alternatively, as per the documentation of mysql, following should work -
SET PASSWORD FOR 'jeffrey'@'localhost' = PASSWORD('cleartext password');
FLUSH PRIVILEGES;
The last line is important or else your password change won't take effect unfortunately.
EDIT:
I ran a test in my local and it worked -
mysql> set password for 'test' = PASSWORD('$w0rdf1sh');
Query OK, 0 rows affected (0.00 sec)
Mine is version 5. You can use following command to determine your version -
SHOW VARIABLES LIKE "%version%";