The big mystery, the lab supplies clue, 9-across, has already been settled in the comment, and in my mind, it’s DA just being nasty. Now to the rest of my confusions:
20 down: Hurt, hearing rock in record (9)
The only way I get close to explaining this is to think record = cd and suppose that somehow hearing rock = hagrine. Am I accidentally correct?
3 down: Like rainbows — or one band — embodying speed of light (5)
I get like rainbows = arced and I get speed of light = c, but I’m not sure why one band = ared or one band = a red.
10 across: Harmonious lady radical concealed her spots (7)
I understand this one completely: lady radical concealed her spots = lady radical – ad – ad = lyrical = harmonious. The question: why are the two instances of ad considered the ‘spots’ to be removed?