do somebody/something a power/world of good
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.
do (one) a/the world of good
To have a very positive effect on someone or something. If you're feeling sad, getting out in the sunlight should do you a world of good.
do someone a power of goodand 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.