Just two left in the bottom right-hand corner, so I think I have something wrong.
11D Ireland certainly produces vengeful women (7) - E?I?S?S
15D A bird found on South Pacific island group (5) - S?T?A
SITTA (a Nuthatch) fits for 15D but I can't parse the "South Pacific island group" which could be SAMOA.
I have absolutely no idea at all about 11D.
The fifth letter of 11D and the third letter of 15D come from:
18A Tuber recedes in early spring (3) - for which I have SET (hidden in the clue backwards).