We report the discovery of a double-peaked Lyman-alpha (Ly alpha) emitter (LAE) at z = 3.2177 +/- 0.0001 in VLT/MUSE data. The galaxy is strongly lensed by the galaxy cluster RXC J0018.5+1626 recently observed in the RELICS survey, and the double-peaked Ly a emission is clearly detected in the two counter images in the MUSE field of view. We measure a relatively high Ly alpha rest-frame equivalent width (EW) of EWLy alpha, 0 = (63 +/- 2) angstrom. Additional spectroscopy with Gemini/GNIRS in the near-infrared (NIR) allows us to measure the H beta, [O III] lambda 4959 angstrom, and [O III] lambda 5007 angstrom emission lines, which show moderate rest-frame EWs of the order of a few similar to 10-100 angstrom, an [O III] lambda 5007 angstrom/H beta ratio of 4.8 +/- 0.7, and a lower limit on the [O III]/[O II] ratio of >9.3. The galaxy has very blue UV-continuum slopes of beta(FUV) = -2.23 +/- 0.06 and beta(NUV) = -3.0 +/- 0.2, and is magnified by factors mu similar to 7-10 in each of the two images, thus enabling a view into a low-mass (M-* similar or equal to 10(7.5) M-circle dot) high-redshift galaxy analogue. Notably, the blue peak of the Ly alpha profile is significantly stronger than the red peak, which suggests an inflow of matter and possibly very low H I column densities in its circumgalactic gas. To the best of our knowledge, this is the first detection of such a Ly alpha profile. Combined with the high lensing magnification and image multiplicity, these properties make this galaxy a prime candidate for follow-up observations to search for LyC emission and constrain the LyC photon escape fraction.