  We present Atacama Large Millimetre Array and Atacama Compact Array
observations of the Sunyaev-Zel'dovich effect in the z = 2 galaxy cluster Cl
J1449+0856, an X-ray-detected progenitor of typical massive clusters in the
present day Universe. While in a cleaned but otherwise untouched 92 GHz map of
this cluster, little to no negative signal is visible, careful subtraction of
known sub-millimetre emitters in the uv plane reveals a decrement at 5$\sigma$
significance. The total signal is -190$\pm$36 $\mu$Jy, with a peak offset by
5"-9" ($\sim$50 kpc) from both the X-ray centroid and the still-forming
brightest cluster galaxy. A comparison of the recovered uv-amplitude profile of
the decrement with different pressure models allows us to derive total mass
constraints consistent with the $\sim$6$\times$10$^{13}$ M$_{\odot}$ estimated
from X-ray data. Moreover, we find no strong evidence for a deviation of the
pressure profile with respect to local galaxy clusters, although a slight
tension at small-to-intermediate spatial scales suggests a flattened central
profile, opposite to what seen in a cool core and possibly an AGN-related
effect. This analysis of the lowest mass single SZ detection so far illustrates
the importance of interferometers when observing the SZ effect in high-redshift
clusters, the cores of which cannot be considered quiescent, such that careful
subtraction of galaxy emission is necessary.
