  We investigate the role of a dynamical gluon in the pion within the Basis
Light-Front Quantization (BLFQ) framework and compare it with the solution of
the Minkowski space Bethe-Salpeter equation, focusing on contributions beyond
the valence state. Particularly in BLFQ, we identify the effect on the pion
structure of the dynamical chiral symmetry breaking by the enhancement of the
spin-flip matrix element, through the $|q\bar qg\rangle$ component of the
light-front wave function and associated gluon parton distribution function
(PDF). We explicitly show an enhancement of the low-$x$ contribution in the
quark PDF associated with the large spin-flip matrix element, necessary to
provide the $\pi-\rho$ mass splitting.
