We study an M1.4 class flare occurred shortly after the X9.3-class flare on 2017 September 6 in NOAA active region (AR) 12673 . The flare was well observed by the Expanded Owens Valley Solar Array (EOVSA), the Goode Solar Telescope (GST) at the BBSO, Hinode, and RHESSI. We find a partial eruption of a flux rope in GST H-Alpha images during the flare, with coronal counterparts seen in SDO/AIA images. Microwave spectral imaging observations from EOVSA provide unique measurements of the coronal magnetic field and energy distribution of the nonthermal electrons accelerated to mildly relativistic energies. We compare the location and morphology of the microwave source with H-alpha, EUV, and X-ray data, and discuss implications for energy release and electron acceleration in this flare.