It has to be either: 1. "Ich werde dir später antworten." or 2. "Ich werde dir die Frage später beantworten." You can use "beantworten" only if somebody asked you a question (which you want to answer later on - "später"). The first sentence just means you will reply to somebody (maybe a message or something like that), no matter if it is a question or not.

You got the meaning right, but it has to be: Ich werde dir später antworten.