Model standing orders make no allowance what so ever for a clerk to convene an extraordinary meeting.
Is this a regular occurrence?
Do you have a resolved and published meeting schedule?
It is illogical for a clerk to unilaterally decide (which would exceed their authority anyway) to try and convene a meeting without talking to the chair first anyway.
How can they produce an agenda without chair endorsing it?
What is the reason / subject matter for the meeting?
Is the opposition to the clerk calling the meeting widespread or 1 or 2 people?
Why not just boycott if widespread.
This is indicative of potential broader issues of either a weak chair, ill informed Cllrs and / or an overly dominant employee (clerk)
What does YOUR standing orders say about convening an extraordinary meeting?
MSOs says chair may do so at any time and if, after 7 days of having been asked to do so, in writing, by 2 Cllrs the chair has not called (that just means set the date) for a meeting, then 4 Cllrs May convene a meeting.
Doesn’t mention clerk anywhere in there….
Unless the chair agrees, the clerk is being a lemon and could end up out on a limb….