special issue devoted to a single topic
Used for magazine or periodical issues that focus entirely on one theme, often with the nuance of putting all effort into covering that topic.
This month's special feature is 'Japanese Castles'.
The magazine puts together a special issue on environmental issues once a year.
特集 is a general special feature or section, while 総力特集 implies a more comprehensive, all-out effort on a single topic.
Compound of 総力 (all-out effort) and 特集 (special feature).