Extra-dimensional QCD axion is well motivated by string compactifications and enjoys enhanced protection against quality-violating effects. If present during inflation, however, its quantum fluctuations generate isocurvature perturbations that strongly constrain the inflationary scale. We propose a dynamical suppression mechanism in warped five-dimensional models, where a radion-inflaton coupling sets the radion minimum at small inter-brane separation during inflation, temporarily enhancing the effective four-dimensional axion decay constant. After inflation, the radion minimum shifts to larger separation, restoring the standard QCD axion window. In a warped orbifold GUT with Goldberger-Wise stabilization, this mechanism can satisfy CMB isocurvature bounds while allowing substantially higher inflationary scales { (up to $H_{\rm inf}\sim10^{12}\,\mathrm{GeV}$ for $f_a\lesssim 2\times {10}^{11}GeV$) compared to} conventional pre-inflationary axion cosmology.