MOSFET aren't generally provided with a clamp diode at the gate. They may possibly have ESD protection. Which transistor type you are referring to?
All power MOSFET have bulk (substrate) connected to source and a built-in drain-to-substrate diode, necessary by technology. It's not provided for a particular purpose, but must be considered in circuit design. Sometimes it's helpful. In a standard MOSFET, the diode has slow recovery, which is mostly unwanted. Some transistor types are speeding up the diode by special means.