The performance of solid-state ${}^{229}\mathrm{\text{Th}}$ nuclear clocks depends sensitively on the microscopic environment of the thorium nucleus in the host crystal. Here we reassess the dominant quadrupole-split thorium site in ${}^{229}\mathrm{\text{Th:CaF}}$_2$, which has been assigned to a thorium dimer in recent spectroscopic work. Thermodynamic estimates, density functional theory calculations, and electric-field-gradient comparisons instead favor an isolated $\text{Th}^{4+}}$ substitution on a $^{2+}} site charge-compensated by two nearby fluoride interstitials in a ${90}^{\circ }$ configuration, consistent with earlier literature. The same calculation identifies another defect, also with fluoride interstitials but in a different spatial arrangement, that matches weaker observed spectral lines. The defect responsible for the clock transition therefore features a single $^{229}} nucleus with nearby fluoride ions, rather than thorium aggregation. This defect assignment has implications for achievable linewidths and provides a microscopic basis for reducing broadening in solid-state nuclear clocks.