Tx Richard. I had a couple of wrong letters at 12. They were correct when I entered them. Using Web on my phone I manage somehow to change letters. 13. I knew the singer but when tried to parse it I missed the (5,5) definition. Clever clue.
Warden re 19, it might not be obvious without a bit of GK.
First five letters are a card game - a scam, in fact. The back half of the answer is the usual "grand" letter surrounded by a historical tyrant from what is now modern day Italy.