Context : Aims : We investigate the properties of cluster ClG 0332-2747 at z=0.734 in the GOODS-South field , which was undetected in the Chandra 2Ms observations . We explore possible scenarios to explain the discrepancy between its low X-ray emission and that expected from the M - L _ { X } relation . Methods : We use the large public spectroscopic database available in the GOODS-South field to estimate the dynamical mass and the virialization status of ClG 0332-2747 . Cluster members selected from their photometric redshift are used with spectroscopic ones to analyse the galaxy population of the cluster . In the newly released Chandra 4Ms observations we detect a faint extended X-ray emission associated to the cluster . Finally , we compare the optical and X-ray properties of ClG 0332-2747 with the predictions of a well-tested semianalytic model . Results : We estimate the velocity dispersion and the virial mass considering all 44 spectroscopic members , or 20 red-sequence members only . We obtain \sigma _ { v } = 634 \pm 105 ~ { } Km / s , M _ { 200 } = 3.07 ^ { +1.57 } _ { -1.16 } ~ { } 10 ^ { 14 } ~ { } M _ { \odot } in the former case , and slightly lower values in the latter case . The cluster appears to have reached the virial equilibrium : it shows a perfectly Gaussian velocity distribution and no evidence for substructures . ClG 0332-2747 contains a high fraction of bright red galaxies and is dominated by a very massive ( 1.1 \times 10 ^ { 12 } ~ { } M _ { \odot } ) old brightest cluster galaxy ( BCG ) , suggesting that it formed at an early epoch . We detect a faint extended X-ray source centred on the BCG , with a total X-ray luminosity of L _ { X } \sim 2 \cdot 10 ^ { 42 } ~ { } erg~ { } s ^ { -1 } ( 0.1-2.4 keV ) . This L _ { X } is lower by a factor of \sim 10-20 than expected according to the M - L _ { X } relation . We provide a possible explanation of this discrepancy assigning it to the effects of AGN feedback on the ICM : the semianalytic model reproduces the M - L _ { X } relation measured from “ X-ray bright ” clusters , and it predicts a high scatter at low masses owing to heating and expulsion of the cluster gas . Interestingly , the model clusters with an evolved galaxy population like ClG 0332-2747 present the largest scatter in X-ray luminosity . However , the low X-ray emission of ClG 0332-2747 is just marginally compatible with predictions , which indicates that additional feedback effects should be included in the model . Conclusions : We propose a scenario where “ X-ray underluminous ” clusters are explained by the strong feedback effect on the ICM in highly evolved clusters . Our hypothesis can be tested by the combined analysis of the galaxy population and of the X-ray emission in large cluster samples .