The landlord or tenant can pay for the tenant improvements

If a landlord plans to make upgrades to a tenant's apartment, they will usually pay for the tenant to stay somewhere else, like a hotel. While the tenant is gone, their apartment will get new carpet, paint, or whatever else is needed to make it nicer.

In most cases, the tenant is responsible for the lease obligations, including leasehold improvements. If the tenant breaks the lease and fails to pay for the improvements, the subcontractor may have options to recover their payment. They can potentially take legal action against the tenant for unpaid work or file a lien on the property to secure their claim. An attorney specializing in commercial lease disputes can provide more specific advice based on the circumstances.

TI = Tenant Improvements

The Tenant Improvement (TI) Allowance is the amount of renovation costs that a landlord is willing to pay based on the agreed upon lease terms on behalf of a tenant. The tenant's build-out/renovations may cost more than the TI allowance in order to meet the tenant's needs/desires. However, the TI Allowance is the limit the landlord is willing to contribute.

Given the wording of your lease, it would only apply to those betterment's and improvements that are non-structural.