WordNet sense 1 (understanding of the nature or meaning or quality or magnitude of something):

appreciation, hold

WordNet sense 2 (the limit of capability):

compass, range, reach

WordNet sense 3 (a firm controlling influence):

grip

WordNet sense 4 (hold firmly):

hold on

WordNet sense 5 (the act of grasping):

clasp, clench, clutch, clutches

WordNet sense 6 (get the meaning of something):

apprehend, comprehend, dig, savvy, grok, get the picture