From Longman Dictionary of Contemporary Englishtighten your grip/hold on somethingtighten your grip/hold on somethinga) to control a place or situation more strictly Rebel forces have tightened their hold on the capital. b) to hold someone or something more firmly Sarah tightened her grip on my arm. → tighten
Examples from the Corpus
tighten your grip/hold on something• The suspended despair inside her splintered into a shuddering sob and Fernando tightened his hold on her.• However, planning permission is required, and legislation is tightening its grip on mast sites.• Oats tightened his grip on the axe.• There were months of interrogations, torture and repression as the military tightened its grip on the country.• It was only when they tensed, curling and tightening their grip on the floor, did he realise they were alive.• They tightened their grip on the girl.• His arm shook and he tightened his grip on the stock of the rifle to still it.• He tightened his grip on the sub-machine-gun, waited for the helicopter to slow and swing towards him. 