Combina dos consultas mysql en una

No puedes ORDER BY en tu primer SELECT y luego UNION eso.

Editar
Sin embargo, puedes

como en la documentación de MySQL UNION

(SELECT a FROM t1 WHERE a=10 AND B=1 ORDER BY a LIMIT 10)
UNION
(SELECT a FROM t2 WHERE a=11 AND B=2 ORDER BY a LIMIT 10);

Lo que luego hace que su SQL

(SELECT clicks FROM clicksTable WHERE clicks > 199 ORDER BY clicks ASC LIMIT 1)
UNION
(SELECT clicks FROM clicksTable ORDER BY clicks DESC LIMIT 1);

Editar 2
Para regresar en una array

SELECT (SELECT clicks 
        FROM clicksTable 
        WHERE clicks > 199 
        ORDER BY clicks ASC 
        LIMIT 1) AS NextClick,
       (SELECT clicks 
        FROM clicksTable 
        ORDER BY clicks DESC 
        LIMIT 1) AS TopClick;