From Longman Dictionary of Contemporary Englishfor dear lifefor dear lifewrittenVERY if you run, fight, hold on etc for dear life, you do it as fast or as well as you can because you are afraid She grasped the side of the boat and hung on for dear life. → dear
Examples from the Corpus
for dear life• Sherman held onto the bar for dear life.• The girl shut her eyes and gripped back for dear life.• The playing throughout the evening was truly superb, every instrumentalist bowing and blowing and thumping as though for dear life.• They often looked very strained to Anna, as if they were holding on to their loyalty for dear life.• With difficulty, he made his way towards her, Charlotte clinging to him for dear life.• It turns on to its side and as I cling on for dear life I hear a startled cry from Nathan.• This wasn't easy either, because she was spooked and was clinging for dear life to the poor kid's hair. 