Is there any way to moderate specific topics i.e. require moderator to approve before it becomes visible to the community?
In terms of site settings the option
approve unless trust level would allow you to require all posts from users below a specific trust level be approved. There’s also an
approve new topics unless trust level which has the same affect for topics. If you set that to TL0 all new users would need their topics or replies to be moderated site-wide before they appear.
You can also require moderator approval of all new topics and replies at a category level. If you look at your category settings under the ‘settings’ tab the options are called
require moderator approval of all new topics and
require moderator approval of all new replies.
There are no equivalent settings to apply to specific topics.