I actually solved on paper in about 30 mins. 11 across should be clued as (4,3) and 12 down should be (5). I really enjoyed the clues for 13 A and especially 15D. Nice job.
It's a cryptic defintion. Elvis's was known for saying thank you very much. Zoomers, gen z, who do be on they phones, would text tyvm instead of saying it.