This part of the 1838 Pluralities Act has never been repealed:
'in all cases where the term “benefice” is used in this Act, the said term shall be understood and taken to mean benefice with cure of souls, and no other (unless it shall otherwise appear from the context), and therein to comprehend all parishes, perpetual curacies, donatives, endowed public chapels, parochial chapelries, and chapelries or districts belonging or reputed to belong, or annexed or reputed to be annexed, to any church or chapel, anything in any other Act to the contrary notwithstanding.'
I like the phrase belonging - or reputing to belong, or annexed or reputed to be annexed to any church or chapel.
'Reputed to belong / to be annexed' covers a mutitude of situations.
The obverse is the obvious - if a parish or district belongs in one benefice by repute, or annexation, it does not belong in the benefice that is was annexed from, or no longer belongs to by repute / reputation.
The application of this is clear as mud - where a cluster is formed by whatever process, and a parish or district is clustered to another it is as if the clustered parish or district belongs to the benefice which it is clustered with.
Formation of clusters of parishes : if you don't want to appoint a vicar to a parish, and don't feel like sequestering the living, cluster the parishes together and create in people's minds the belief that they belong together.
If you wish to avoid being clustered your freedom of action is to appeal to the Archbishop to present an incumbent to the benefice, once the parish has been vacant for a 6 month period.
Alternatively just say no thank you... but that might not work.
Clusters allow both abrogation and arrogation without sequestration.