Aim: In this work package we will answer the question: what is the best use of the cluster member spectroscopic data to enhance the Euclid cluster cosmology? How can we use spectroscopic data to inform the scaling relation and thus improve the constraining power of the cluster sample? A promising venue to overcome systematics in the cluster mass calibration is by means of multi-wavelength data (e.g. [Co21]). Mass proxies derived from data at different wavelengths are subject to different sources of systematics, and thus can be used to enhance the scaling relation calibration. Euclid will provide ~10,000 clusters with enough spectroscopic data for member galaxies (~10 or more) that can be used as an (additional) mass-proxy to calibrate the cluster masses, in the redshift range 0.9≲z≲1.8, where other mass proxies become ineffective (weak lensing and X-ray-based) . Preliminary analyses based on Euclid survey mocks from the GAEA simulations indicate that we will be able to calibrate the scaling relation between cluster velocity dispersion and cluster masses with a fractional uncertainty of 30%.