A few pointers would be gratefully received:
5. Metaphorically Edward 1 used this (6)
8. You won't need to run fast to catch this piece of church architecture (7,5)
16. What has none in 2012 but may have 7s in 2016? (5)
19. This bird lacked success (5,3,5)
20. a useful sportsman after 3rd January storm! (6)