。
I'm afraid of what the teacher will say.
Literal
I [topic-は] teacher [subject-が] what [quotative-と] say-[question-か] afraid.
An embedded question: 先生が何と言うか ('what the teacher will say') is an indirect question, with か marking it as an interrogative. 恐い (also written 怖い) = 'scary, afraid' — an い-adjective. The embedded question functions as the (unmarked) object of the adjective.