Thanks, Jon. While it is a term that I am not familiar with, I still should have gotten it from the wordplay, except I had misspelled 23a. No wonder I was having so much trouble. No word in Chambers seemed to match. Not my best moment. 😖
I can't work out where the W comes in for 2D though... I got the first 2 letters from a clue the other week which also used that for "on horseback", but maybe I am missing something.