That's what the BEC is for. It steps the voltage down to a usable level.
https://www.castlecreations.com/en/cc-bec-010-0004-00
Up to 6S input with output adjustable from 4.8-9V. I ran one of those for a while in my e-revo until I upgraded the esc. I ran it off the full input voltage to the esc...