The Collaborative International Dictionary
Improving lease
Improving \Im*prov"ing\, a. Tending to improve, beneficial; growing better. -- Im*prov"ing*ly, adv.
Improving lease (Scots Law), an extended lease to induce the tenant to make improvements on the premises.
Wiktionary
improving lease
n. (context legal Scotland English) An extended lease to induce the tenant to make improvements to the premises.