There are no such things as 'senior councillors - except perhaps in age. All members of a council are equal. If there are a sufficient number of members wishing to see the clerk's conduct examined then such a matter can be voted through. If there are not, then it might be difficult to make headway within the council itself but if the alligations have any foundation it would seem highly likely that there are breaches of the Code of Conduct by members. Such matters should be referred to the Monitoring Officer of your primary council.