Hi, gazzar, glad to read that you are persevering with the puzzle.
In 12ac, you are looking for an old-fashioned word for a popular green vegetable, the first three letters of which sound like the more common name for the vegetable. In the wordplay, “are” leads to the abbreviation for a metric measure of area, “very good” implies a two-letter interjection, and these are inside a term for a female swan, if the male swan is a hob.
In 15dn, CFS is chronic fatigue syndrome, which has an alternative name with a two-letter abbreviation. This is reversed and goes round the standard abbreviation for “lecturer”, giving a tree known for suffering from disease.
In 22dn, nudists have nothing on, so they can’t have ... The symbol is in the cell with number 22, but it symbolises a word with the same meaning as the word it symbolises in 21ac.
I’m just home from my last day at work until after Easter. I’m also going to have to tackle the garden!