The Council have the ultimate responsibility in ensuring everything is legal. However, the Clerk by the very nature of her role should ensure this is just so and one would expect the auditor may pick up on this as part of the governance review. If the Clerk fails to action such matters or reports back to the PC then performance management proceedings should be started.
Of course, the Clerk may not be completely aware of all the governance and can seek advice from the local associations, Clerk, SLCC, auditor or solicitor (Who may be on a retainer from the borough/County council).