totally stuck on the last 4
25A : Pawn and rook I win, playing chess - or bishop, perhaps (7) : ??I???E
26A : Finishes off crossword puzzle on Sunday for contest (4) : D?N?
20D : reduce severity of clot you reported, over time (7) : A?S???E
21D : Harden or soften (6) : ?E???R
Many thanks in anticipation