Notwithstanding the definition of format the procedure of a Parish meeting is that the parish council is required by law to hold one parish meeting per year, A Parish meeting at any time can be called at the request of six members(electorate) of the community. The request must be made to the parish council (because they are required to organise, advertise and meet the cost of the meeting) . As this is a meeting of the members of the parish then those applying should provide an agenda which should be published by the PC within the same requirements of a parish council meeting. Chairmanship of the meeting falls to the PC chair and in their absence (and of vice chair) a chair can be elected from the floor of the meeting. Only registered voters of the parish are allowed to speak or vote at a parish meeting. Any topic regarding the parish can be on the agenda and decisions made and voted on may request action or answers from the parish council.
Do not confuse a parish council meeting and a parish meeting which are completely different matters. The parish council has no authority over a parish meeting but do have over a parish council meeting.
So, if you have matters that require resolving then a parish meeting can "focus" the parish council on matters for their action.