、。
There are some oranges on the tree.
Literal
Tree [on-には], oranges [subject-が] several are-fruiting.
なる here is the verb 生る/成る ('to bear fruit, to grow [on a tree]'), not the more common なる ('to become'). In ~ている form it describes the ongoing state of fruit being present on the tree. いくつか ('several') is the vague quantifier. The に-は composite marks the tree as a located, topicalised context.