I am a word of five letters Riddle

I am a word of five letters!
People eat me!
If you remove my first letter i will be a form of energy!
If you remove my first 2 letters i will be needed 4 living.
If you remove my first 3 letters i will be a preposition
If you remove my first 4 letters i will be a drink 4 u.
Answer if you are mastermind!

 

 

 

 

 

 

 

 

 

 

 

 

 

Solution: WHEAT