Gauging Conformal Algebras with Relations between the Generators

We investigate the gauging of conformal algebras with relations between the generators. We treat the $W_{5/2}$--algebra as a specific example. We show that the gauge-algebra is in general reducible with an infinite number of stages. We show how to construct the BV-extended action, and hence the classical BRST charge. An important conclusion is that this can always be done in terms of the generators of the $W$--algebra only, that is, independent of the realisation. The present treatment is still purely classical, but already enables us to learn more about reducible gauge algebras and the BV-formalism.