Black has exposed his King. Black on the move might procure a safe retreat for the King to X2 by advancing P-X3. If White is to move, he wins.
1 R-Kt6ch.
K-K2
2 R-R7ch.
K-K1 (best)
3 R-Kt8ch.
Q-Q1
4 RxQch.
KxR
(!wi]
5 R-R8ch.
K moves, say
5 ... K-Q2
[!!wi)
6 RxR and wins by plus of pieces.