CATCH ON TO is a phrase that means to understand or comprehend something. The crossword solutions for this term are GRASP (5 letters), GET (3 letters), TWIG (4 letters), and GETWISE (7 letters). GRASP implies a physical action, as if one is reaching out to grab something. GET implies a more general action of obtaining something. TWIG suggests understanding something quickly, as if one has suddenly realized something. Finally, GETWISE implies gaining knowledge or wisdom.