Please Can Someone Help-Cryptic

[citygirl2013]

15 a sportingly, this side doesdrop of sea watersnt accept a paying proposition
amateurt???
4d those on this roll may make their mark
blacko???
19a drop of sea water
???
16d around, or a series of rounds
???u?
my brain cant fathom these ones and they are probably so simple. I would appreciate your expertise. Thank you

[mac44]

16d. about, a bout.

[boxtops]

4d blackouts?

[boxtops]

19a Ebb (tide, sea level drops)

[boxtops]

16d a bout

[boxtops]

should 15 say

15 a sportingly, this side doesnt accept a paying proposition

(looks like the "drop of sea water" has dropped into the clue!)

[boxtops]

if so - amateur team ??

[citygirl2013]

Thank you for making those clear to me. that leaves one.
sportingly this side doesnt accept a paying propositionn
amateurt?t?
You are all stars, many thanks