From Longman Dictionary of Contemporary Englishstumbling blockˈstumbling ˌblock noun [countable] a problem or difficulty that stops you from achieving somethingstumbling block to The main stumbling block to starting new research is that we lack qualified people.
Examples from the Corpus
stumbling block• It is still foolishness and a stumbling block.• They needed the scrupulous professional integrity which nearly proved such a stumbling block to them in this case.• Only rarely is the lack of sufficient minimum capability a real stumbling block to change.• In the autumn of 1987, Conran ran into a potentially more serious stumbling block to his plans.• The stumbling block is a case challenging the constitutionality of the new law. 