I'm embarrassed to be back. Two to finish.
21a A piece of music (low notes) required for the tumbler (5) -l-w-
18d Use the horn as well near the end of the street (4) e-o-
No need for embarrassment I do crosswords every day and I find this one sometimes the most tricky of them all,I am obviously not in the mindset of the setter,glad to help and good luck.