Q.

Its a 6 letter word.

– First 3 letter indicate something  big  on earth.
– 2, 3, 4 letter indicate parts of human body.
– 3, 4, 5 letter indicate part of circle.
– The whole word is the key of internet now.
101% brain work.  Keep Searching 😉

A.

Search.

Thanks to Pratap Roy and Upendra Kumar for answering it correctly !