Deposit vs Lease Premium

Tenancy Deposits

Hi
As a leting agent we have been asked for some adivce from a landlord who we found a tenant for over 12 months ago. The lock on the outside door to the flat abouve a commercial premises(also owned by landlord) got broken (by who we do not know). Under the tenancy agreement the tenant is responsible for the cost of getting this repaired/replaced. The landlord contacted us to ask he he can take the cost of the repair from the tenants deposit, as they wont agree to paying for it. We advised this would could only be done at the end of the tenancy with the tenants agreement. The landlord has now asked if in future he can include a "lease premium" in the tenancy agreement instead of a deposit. We have never done this for an AST, is this something we/landlord can do, or is this purely a commercial clause?

Many thanks