Stuck in bottom right hand corner, so all help appreciated.
19A - Ship boarded by a soldier about to catch small seals. I have S??ND?S.
20D - Learn what finishes off long list. I have ??EAN. (1st letter of this is 3rd of 19A).
21 D - Chartreuse back on stage quickly ending sad song. I have DIRGE for this, but it may be wrong.