  In the light of the recently observed XENON1T electronic recoil (ER) data, we
investigate the possibility of constraining the parameter space of a generic
fermionic warm dark matter (WDM), decaying into a standard model (SM) neutrino
and a photon. The photon as a decay product, when produced inside the XENON1T
chamber, interacts with an electron of a xenon (Xe) atom, leading to a
contribution in the observed ER data. We add this dark matter (DM) induced
signal over four distinct backgrounds (taking one at a time) and perform a
single parameter $\chi^2$ fit against the XENON1T data to obtain the best-fit
values of the DM decay width and the associated 95$\%$ confidence level (C.L.)
bands for DM mass varied in the range $2 - 18$ keV. By comparing the
constraints, obtained by fitting the XENON1T data, with the upper limits,
arising from various existing astrophysical and cosmological observations, we
find that a fair amount of the DM parameter space is allowed at $95\%$ C.L.,
for each of the background models considered.
