I am a word of 7 letters!
People use me daily!
If you remove my last two letter I will
Be in at your doorstep!
If you remove my first three letters I
Will be near your bed.
If you add a letter at the start I
Will be a sea creature
If you remove my first four letter I
Will be a part of daily living.

I run over fields and woods all day. Under the bed at night I sit not alone. My tongue hangs out, up and to the rear,awaiting to be filled in the morning. What am I