12 month's rent up front - is this a deposit?

Tenancy Deposits

I have a tenant who wishes to rent my property for 12 months on a AST. Due to earnings levels my insurer will not gauantee the rent and so the tenant has offered to pay the whole 12 month's rent up front ( as well as the standard delapidations deposit). I heard mention some time ago that advance rent had to be treated as a deposit and 'protected'. As hope this is incorrect as we lodge all deposits in the dps and trying to release £ x per month from it in order to cover the monthly rental would be impossible. Hopefully i misunderstood the point and, if so, is there a standard line that i can add to the tenancy agreement after the clause - the monthly rental is £ x for 12 months such as ... payable as an immediate payment of (12 X £ x). Many thanks in advance for any help