If you say that something is not a panacea for a particular set of problems, you mean that it will not solve all those problems. Membership of the ERM is not a panacea for Britain's economic problems. something that people think will make everything better and solve all their problems = cure-all panacea for (panakeia, from pan- ( PAN-) + akeisthai )
[ "pa-n&-'sE-& ] (noun.) 1548. From Latin panacēa, from Ancient Greek πανάκεια (panakeia), from πανακής (panakēs, “all-healing”), from πᾶν (pan, “all”) (equivalent to English pan-) + ἄκος (akos, “cure”).