Spoiler for 56D:
The ampersand is a ligature of et, latin for “and”
Hence an acceptable way of writing etc. is &c. I read it first in Hamlet and have not gone back to spelling etc. anymore.
Similarly et al can be abbreviated to &al; plural of the same would give us the answer &ALS. This clue was the reason I couldn't have the puzzle except "&" and (AND) as acceptable. I could have used a different word but I kind of fell in love with &ALS despite the plural form which I generally despise as a rule of thumb