From Longman Dictionary of Contemporary Englishsingleness of purposesingleness of purposeformalDETERMINED great determination when you are working to achieve something → singleness
Examples from the Corpus
singleness of purpose• Fridays Pray for the Mission Board, that there might be unity and a singleness of purpose.• Well-structured courses prevent the sense of singleness of purpose from being dissipated.• Here spoke the man of destiny whose singleness of purpose overrode all other considerations. 