Need 2 to complete, which I can't get at all.
19a: "German composer was accustomed to back involving it" (6) -e-s-u Have searched German conmposers online without success. I assume "used" comes in somewhere?
16d: "Good for Garland, say, but wrong when presented by matinee idol" (8) -i-g-b-e
I thought the end might be "gable" for Clark (!) but can't get the rest if that's right.