do a power of good, to

do (one) a power of good

To be very beneficial to one. If you're feeling sad, getting out in the sunlight should do you a power of good.
See also: good, of, power
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

do someone a power of good

 and do someone a heap of good
Rur. to be very good for someone. You should take a vacation. It'd do you a power of good. Just hearing your voice does me a heap of good.
See also: good, of, power
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

do a power of good, to

To effect a great improvement. This somewhat unsophisticated turn of phrase uses “power” in the sense of “much” or “a great deal.” For example, “Those vitamins will do her a power of good.”
See also: of, power, to
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer
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