Galaxy clusters have long been theorized to quench the star formation oftheir members. This study uses integral-field unit observations from theK-band MultiObject Spectrograph (KMOS) – Cluster Lensing AndSupernova survey with Hubble (CLASH) survey (K-CLASH) to search forevidence of quenching in massive galaxy clusters at redshifts 0.3 <z<0.6. We first construct mass-matched samples of exclusivelystar-forming cluster and field galaxies, then investigate the spatialextent of their H α emission and study their interstellar mediumconditions using emission line ratios. The average ratio of H αhalf-light radius to optical half-light radius ( $r_{\mathrm{e}, {\rm{H}\,\alpha }}/r_{\mathrm{e}, R_{\mathrm{c} } }$ ) for all galaxies is1.14 ± 0.06, showing that star formation is taking placethroughout stellar discs at these redshifts. However, on average,cluster galaxies have a smaller $r_{\mathrm{e}, {\rm {H}\alpha}}/r_{\mathrm{e}, R_{\mathrm{c} } }$ ratio than field galaxies: <$r_{\mathrm{e}, {\rm {H}\alpha }}/r_{\mathrm{e}, R_{\mathrm{c} } }$ >= 0.96 ± 0.09 compared to 1.22 ± 0.08 (smaller at a 98 percent credibility level). These values are uncorrected for the wavelengthdifference between H α emission and Rc-band stellarlight but implementing such a correction only reinforces our results. Wealso show that whilst the cluster and field samples followindistinguishable mass–metallicity (MZ) relations, the residualsaround the MZ relation of cluster members correlate with cluster-centricdistance; galaxies residing closer to the cluster centre tend to haveenhanced metallicities (significant at the 2.6σ level). Finally,in contrast to previous studies, we find no significant differences inelectron number density between the cluster and field galaxies. We usesimple chemical evolution models to conclude that the effects of discstrangulation and ram-pressure stripping can quantitatively explain ourobservations.