With the pawn only on the fourth rank and the king cut off by a single file, the defender holds by placing the rook in front of the pawn and checking from the front whenever the attacking king steps forward.
Black's king has been cut off on the f-file by the rook on e1, but the pawn is still on d4. That one detail saves Black: a pawn on the fourth with the king cut off by one file is a draw, and the method is the frontal defence. The rook on d8 stares down the d-file, so the white king can never step onto d5 and the pawn can never advance with support.