We report on the determination of the improvement coefficient $c_{{\rm A}}$ for the non-singlet axial-vector current $A^{a}_{\mu}(x)$ in the framework of stabilised Wilson-Clover fermions within three flavour lattice QCD. This is done by requiring the PCAC relation to hold for two different pseudo-scalar states. To generate these states, wavefunctions altering spatial structures on the boundaries of a Schrödinger functional lattice are employed and some variations of the (previously applied) wavefunction method are explored. The improvement coefficient is determined on a few ensembles for a range of gauge couplings that is potentially useful for future applications. Preliminary results on the renormalisation constants $Z_{{\rm V}}$ for the vector current and $Z_{{\rm A}}$ for the axial-vector current are also presented.