Output powers as high as $300\mathrm{mW}$ were obtained at $1925\mathrm{nm}$ in the cw regime with a Tm laser operating at room temperature, either with Ti-sapphire or diode laser pumping, using a new single crystal of $\mathrm{NaGd}({\mathrm{WO}}_4{)}_2$ grown by the Czochralski method and doped with $5\mathrm{mol}.\%$ of ${\mathrm{Tm}}^{3+}$ in the melt. This crystal belongs to the $I\overline{4}$ tetragonal space group and exhibits a locally disordered structure due to the random occupancy of the same lattice sites by Na and Gd (or Tm) ions. The local disorder results in large bandwidths of the ${\mathrm{Tm}}^{3+}$ optical transitions (e.g., $\mathrm{FWHM}\approx 60{\mathrm{cm}}^{-1}$ at $5\mathrm{K}$ for the ${}^{3}H_6\to {}^{3}F_4$ transition involved in the laser emission), which allows one to obtain one of the broadest laser tunability ranges, from 1813 to $2025\mathrm{nm}(\approx 17\mathrm{THz})$ , achieved with a ${\mathrm{Tm}}^{3+}$ -doped crystalline material. A detailed characterization of the ${\mathrm{Tm}}^{3+}$ optical spectroscopy in this novel host was performed at 5 and $300\mathrm{K}$ .