We demonstrate a method for measuring the anisotropy of a side group liquid crystalline polymer (SGLCP) in a perdeuterated nematic solvent using small-angle neutron scattering. In this system scattering originates from both the polymer backbone and the large pendant side groups, causing the measured anisotropy to vary with molecular weight. Since it is the backbone anisotropy that is of interest, we show how to mathematically account for scattering due to the side groups. Using a molecular weight series of SGLCPs that have an oblate conformation, this method yields a constant ratio of the backbone radii independent of molecular weight and spacer length.