• I am witch on a beach (8): sandwich
• Zoro hit me twice a quarter after 3. (5): pizza (pi is after 3, two zz from zorro's sword)
• Hand me a bag of 50 (5): bagel (L is roman numeral for 50)
• Get a spa with a tea (8): spaghetti (spa, get + tea). This is 9, but I think it is correct.
• Witch misses the stake (7): mistake
• I am in terror (5): error (is in the word terror)
• I are not a giraffe (5): gaffe (means a mistake, a blunder) - take the I and R (are) out of giraffe.
• Flair with no err (4): remove the "r" from "flair" and you have an anagram of fail, err sounds a bit like "r", could also refer to "failure" (fail + err)
Traits / attributes necessary to be good at something
• Let it be rain (5): brain (B+rain) - I wasn't convinced by this, but @MOehm made a decent case for it.
• Say no legend (9): knowledge (say "no legend" and you hear knowledge)
• End the tall (6): talent (tall + end)
• Kill the snake (5): skill the s is like a snake, and added the kill.
Final group, least certain here:
Relating to living arrangements
• Oh, no R. (5): owner (thanks for the freebee - as soon as you told me it was so obvious!)
• A ghost has no age (4): host (take a "g" out of ghost)
• Who would have guessed? (5): guest
• Ten ants running on the floor. (6): tenant