here is a simple way of distinguishing between whether a bond is covenant ionic or metallic. if a metal and a non-metal chemically bonded then they're ionic. if a non-metal and a no-metal chemically bonded they're covalent and if a metal and metal bonded they're metallic. in your case Cl and O are both non-metals hence they are covenant.
Ans. Covalent bond.
The most common type of chemical bonding is covalent bonding. Covalent bonding arises when two, or less often a different number of, electrons are shared between two or more atoms. For example, in the molecule (Cl2O), each chlorine atom originally has 7 electron; in the molecule, it shares one pair of electrons with the oxygen atom. The second electron of each pair originally belonged to the oxygen. The remaining four electrons in the outer orbitals of the oxygen, In most normal covalent bonding, each atom contributes one electron per bond of the two electrons required per bond.