A rock cover is a song that is a cover version of an original rock song. The two crossword solutions for the term 'rock cover' are 'MOSS' and 'PAPER'. 'MOSS' is a four letter word that refers to a type of plant that grows in clumps or mats, often in damp or shady locations. 'PAPER' is a five letter word that refers to a thin material made from cellulose pulp, derived mainly from wood, rags, and certain grasses, which is primarily used for writing, printing, drawing, wrapping, and packaging.