It certainly looks to have been built by a spider. I don't think it's a nursery web of Pisaura (nursery web spider) therefore I'm inclined to think it's the retreat, probably with an egg case, of an orb web spinner such as Larinioidescornutus or Araneus quadratus. Occasionally they can be some distance from the main part of the web.
Cheiracanthium erraticum comes with the common name the Grass Head spider and makes a retreat come egg cocoon in grass heads stitched together. They can look quite different depending on what grass heads or leaves they have used. They only way to be sure would be to winkle the spider out - be careful if it is Cheiracanthium though as they have large and powerful fangs and can deliver a shocking bite with painful symptoms.