Amplification in a single-clad, large-mode-area erbium fiber as an alternative to double-clad Er-Yb amplifiers is presented. Both signal and pump are coupled through a mode-matched splice into the fundamental mode, which ensures preferential gain in the fundamental mode while minimizing the amplified spontaneous emission (ASE). The $875\mu {\mathrm{m}}^2$ effective area of the Er fiber enables amplification of $6\mathrm{ps}$ pulses at $1.55\mu \mathrm{m}$ wavelength by $\sim 33\mathrm{dB}$ in a single stage to $>25\mathrm{kW}$ peak power with low nonlinear pulse distortion and a diffraction-limited output beam with $M^2<1.1$ .