What is "ringfence"

n. A fence which encircles a large area, or a whole estate, within one enclosure. vb. 1 (context transitive English) to guarantee the safety of funds or investment. In particular, to ensure some degree of distinction for monies, that may provide immunity against untoward financial claims. 2 (context transitive English) to specify that funds may only be used for a specific purpose, especially government funds