con·serve • v. / kənˈsərv/ [tr.] protect (something, esp. an environmentally or culturally important place or thing) from harm or destruction: the funds will help conserve endangered meadowlands. ∎  prevent the wasteful or harmful overuse of (a resource): industry should conserve water. ∎  Physics maintain (a quantity such as energy or mass) at a constant overall total. ∎  (usu. be conserved) Biochem. retain (a particular amino acid, nucleotide, or sequence of these) unchanged in different protein or DNA molecules. ∎  preserve (food, typically fruit) with sugar.• n. / ˈkänˌsərv/ a sweet food made by preserving fruit with sugar; jam.

conserve vb. XIV. — (O)F. conserver — L. conservāre; see CON- (intensive) and SERVE.
So as sb. †preservative XIV; medicinal or confectionary preparation XVI. — (O)F., f. the vb. conservation XIV. — (O)F. or L. conservative preservative XIV; (in politics) XIX; hence conservatism XIX.