How dare the robins sing
settled with the year
Accounting metaphor—death as paying off a debt. The dead have "settled their account" with life, like closing out a ledger at year's end.
consummate bill
"Consummate" means complete or final. Death is the total sum of everything life charged them—paid all at once, account closed.
Beguiled of immortality
"Beguiled of" means tricked out of or cheated of. The dead person was deceived—promised eternal life but got darkness instead.
garden wrestles with the dew
Dawn imagery—flowers struggling to lift their heads under the weight of morning dew. Life keeps fighting even when death should stop everything.