Cells are covered in it, in brief Crossword Clue

 The answer to the crossword clue "cells are covered in it, in brief" is MEMBRANE.

A membrane is a thin layer of tissue that covers or encloses an organ or other structure. In the case of cells, the membrane is called the plasma membrane. The plasma membrane is a selectively permeable membrane, which means that it allows some substances to pass through it while blocking others. This allows cells to control the substances that enter and exit the cell.

The plasma membrane is also responsible for maintaining the cell's shape and for protecting the cell from its environment. It is a vital part of the cell, and without it, cells would not be able to function properly.

The crossword clue "cells are covered in it, in brief" is a good way to remember the importance of the plasma membrane. It is a brief way to describe something that is essential to the function of cells.