I am a word of five letters!
People eat me!
If u remove my 1 letter i will be a form of energy!
If u remove my first 2 letters i will be needed 4 living.
If u remove my first 3 letters i will be a preposition
If u remove my first 4 letters i will be a drink 4 u.
Answer if u r mastermind!
Wheat. Many thanks to Suresh Kumar G for prompt answer (comments below)