Per
Area is one such word.
Words that start with R and end with Y are:racyrainyrallyraspberryraspyratifyrayreadilyreadyreallyrecoveryrectoryregencyregistryrelayrelyriskyrosaryrosyrowdyroyaltyrubyruddyrudelyrunwayrusty
Brother.
rhombus
Salamander.
roadster
Five letter words that start and end with R:radarrazorrecurreferricerriderrigorriverrotorroverrulerrumor
The only word that starts with R and ends with J is 'RAJ'.
Six letter words that start and end with R:rafterraiderrancorrangerrapierraptorrasherratherreaderreaperrectorreeferrenderrenterrepairricherrigourringerripperrobberrockerrollerromperrooferrosterrubberrudderrunner
Clover, clever, closer and closer is a 6 letter word. They begin with CL and end with R.
ruing
A simple example is "ricin".