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SAGE1C\,J053634.78$-$722658.5 is a galaxy at redshift $z=0.14$, discoveredbehind the Large Magellanic Cloud in the {\it Spitzer} Space Telescope"Surveying the Agents of Galaxy Evolution" Spectroscopy survey (SAGE-Spec). Ithas very strong silicate emission at 10 $\mu$m but negligible far-IR and UVemission. This makes it a candidate for a bare AGN source in the IR, perhapsseen pole-on, without significant IR emission from the host galaxy. In thispaper we present optical spectra taken with the Southern African LargeTelescope (SALT) to investigate the nature of the underlying host galaxy andits AGN. We find broad H$\alpha$ emission characteristic of an AGN, plusabsorption lines associated with a mature stellar population ($>9$ Gyr), andrefine its redshift determination to $z=0.1428\pm0.0001$. There is no evidencefor any emission lines associated with star formation. This remarkable objectexemplifies the need for separating the emission from any AGN from that of thehost galaxy when employing infrared diagnostic diagrams. We estimate the blackhole mass, $M_{\rm BH}=3.5\pm0.8\times10^8$ M$_\odot$, host galaxy mass,$M_{\rm stars}=2.5^{2.5}_{1.2}\times10^{10}$ M$_\odot$, and accretionluminosity, $L_{\rm bol}({\rm AGN})=5.3\pm0.4\times10^{45}$ erg s$^{-1}$($\approx12$ per cent of the Eddington luminosity) and find the AGN to be moreprominent than expected for a host galaxy of this modest size. The old age isin tension with the downsizing paradigm in which this galaxy would recentlyhave transformed from a star-forming disc galaxy into an early-type, passivelyevolving galaxy.

An evolutionary missing link? A modest-mass early-type galaxy hosting an over-sized nuclear black hole