I wouldn't really expect the clerk to intervene in relations between councillors, although they can be supportive in giving advice on the legal and practical position. There is no way to get rid of a bad chairman except at the annual meeting, and then it requires a majority of councillors to support an alternative candidate.
The only simple answer is to resist bullying. Council members (including chair and vice chair) have no rights over other councillors, and all council decisions must be made in council meetings by a vote. Thus, every member is entitled to stick to their guns and cast their votes as they see fit. Whether debate is discussed in a fair and reasonable manner is another matter, as it is difficult to cope with a bad chairman.