A stiff challenge but good fun nonetheless.
FOI was 10a followed by 11a.
If you do get stuck there is at least one long anagram in both the acrosses and downs.
Philistine that I am, I was unaware of the Tennyson reference but given the crossers and definition, it could only be one word which I then put into Google alongside Tennyson and Hey Presto!
9a - This is the only parsing I'm not sure of although I am sure of my answer. The best I can come up with is that a 4 letter "replaces" is reversed and then followed by "nothing" and "right". My problem is that there is no reversal indicator so wonder if that's why the question mark is there - or I've completely misunderstood it!
COD - Joint winners this week with 7d and the witty image it evokes and the wonderful 14d.
Thanks to Imogen for a most enjoyable challenge.
Congratulation to Forum regular Chris who celebrated his Golden Anniversary last weekend.
Welcome to new poster Nuncio.
Stay safe:-)