  Within the Basis Light-Front Quantization framework, we systematically
investigate the subleading twist (twist-3) transverse-momentum-dependent parton
distribution functions (TMDs) of the proton beyond the Wandzura-Wilczek (WW)
approximation. The subleading twist TMDs are not independent and can be
decomposed into twist-2 and genuine twist-3 terms from the equations of motion.
The latter involves quark-quark-gluon correlations and contains interferences
between two light-front Fock sectors, $|qqq\rangle$ and $|qqqg\rangle$, which
are usually neglected in the WW approximation.
