Most known quasars at z>6 were selected through their rest-frame UV emission. Only a small number of reddened quasars have been identified at these redshifts, leaving their nuclear and host-galaxy properties poorly constrained. We present JWST/NIRSpec spectroscopy and ALMA band 6 observations of the quasar J1440+0019 at z=6.5488, revealing its dust-reddened nature and jointly characterizing its nucleus and host galaxy. The continuum is best described by an SMC-like extinction law with E(B-V)=0.20±0.03. Three absorption systems detected in N V, Si IV, and C IV are blueshifted by approximately 900--3600 km s⁻¹ and likely trace an ionized nuclear outflow. The broad Mg II line and extinction-corrected continuum yield a black-hole mass of log(M_(rm BH)/M_⊙)=9.04±0.42, a bolometric luminosity of L_(rm bol)≃1.1×10⁴⁷ erg s⁻¹, and an Eddington ratio of λ_(rm Edd)≃0.8. ALMA observations further reveal its host galaxy to be among the most [C II]-luminous known at z>6, with L_([C II])=(7.21±0.25)×10⁹ L_⊙. For a fiducial dust temperature of 47 K and emissivity index β=1.6, the dust continuum implies L_(rm TIR)=8.9×10¹² L_⊙ and M_(rm dust)=4.0×10⁸ M_⊙. The inferred dynamical mass places J1440+0019 in the region of the M_(rm BH)--M_(rm dyn) plane occupied by high-redshift blue quasars. These observations reveal a moderately reddened, rapidly accreting quasar in a luminous, dust-rich host during reionization. Its measured nuclear and host-galaxy properties provide an observational reference for identifying and characterizing similar systems in future systematic searches with wide-area infrared surveys.