Sorry, I thought this was poor.
12a obscure writer (who I had heard of, in fact)
16 CLING a valid answer until crossers in
18 both definitions loose
17 what does "for" contribute
21a first 4 letters grated
22 what does "for" contribute (again!)
5 depending on how you parse it, either free or over is doing double duty
12d I dislike Qaos x% clues
16d "shelter" very loose
I was held up on 21d as I had the wrong base for 24a - it nearly works