For this week's spy game, the answer is MARSHMALLOW.

The name Marshmallow is gotten from the MALLOW PLANT (Althaea officinalis), a herb native to parts of Europe, North Africa, and Asia.
According to Wikipedia, Marshmallow is a type of confectionery that is typically made from sugar, water and gelatin whipped to a solid-but-soft consistency. It is used as a filling in baking or normally molded into shapes and coated with corn starch.

The marshmallow plant has a history of use in herbal medicine. However, when mixed with something sweet, the sap of the plant made for a natural ingredient in making confections.

Marshmallow starts with M and is derived from a plant, mallow. It is soft and airy and can be roasted or used as a filling in baking.