Hidden frustration in the triangular-lattice antiferromagnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>NdCd</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">P</mml:mi> <mml:

We report a study of the magnetic ground state and crystal electric field (CEF) scheme in the triangular-lattice antiferromagnet ${\mathrm{NdCd}}_{3}{\mathrm{P}}_{3}$. Combined neutron scattering, magnetization, and heat capacity measurements demonstrate that the ${\mathrm{Nd}}^{3+}$ moments occupying the triangular lattice in this material harbor hidden signs of frustration not detected in typical Curie-Weiss-based parametrization of the frustration index ($f={\mathrm{\ensuremath{\Theta}}}_{CW}/{T}_{N}$). This is evidenced by a zero-field splitting of the Kramers' ground state and first excited state doublets at temperatures far in excess of ${T}_{N}$ as well as signatures of low-energy fluctuations for $T\ensuremath{\gg}{T}_{N}$. A suppression of the zero-field ordered moment relative to its field saturation value is observed, and the impacts of this magnetic frustration as well as the coexisting bond frustration in the CdP honeycomb network on the physical properties of ${\mathrm{NdCd}}_{3}{\mathrm{P}}_{3}$ are discussed.