优先租赁权怎么说？

prior leasehold

优先是指有第一拒绝权力或第一选择权。

“优先租赁权”可翻成：
the first right to lease
the first right to respond to the lease offering
the first right of refusal to leasing
the first right of refusal to the lease offering

这是合同用语。

underlying leasehold/preferential leasehold

underlying
adj.
underlie 的现在分词
在下(面)的, 下层的, 基础的
隐晦的; 潜在的
【律】(债券)优先的; 第一的, (担保、权利等)主要的
adj.在下面的, 根本的, 潜在的, [商]优先的

preferential
adj.
Of, relating to, or giving advantage or preference:
优先的优势或优先权的、与优势或优先权有关的或给予优势或优先权的：
preferential treatment.
优先的待遇
Manifesting or originating from partiality or preference:
优惠的显示或源于偏袒或偏爱的：
preferential tariff rates.
特惠的关税率