We demonstrated a 2.1 µm nanosecond laser pumped, 2.6 µm continuous-wave (CW) seed injected, cadmium selenide (CdSe) signal singly resonant optical parametric oscillator (OPO). A maximum average power of 1.05 W was obtained corresponding to a pulse energy of 1.05 mJ at the idler wavelength of 10.1 µm and optical-to-optical conversion efficiency of 4.69%, beam quality of $M_x^2={2.25}$Mx2=2.25, $M_y^2={2.12}$My2=2.12 and pulse width of 24.4 ns. To the best of our knowledge, this is the first time to achieve 10-12 µm laser with watt-level average power using OPO technology.