newsticker-justification

newsticker-justification is a variable defined in `newst-reader.el'.
Its value is

left

Documentation:
How to fill item descriptions.
If non-nil newsticker calls `fill-region' to wrap long lines in
item descriptions. However, if an item description contains HTML
text and `newsticker-html-renderer' is non-nil, filling is not
done.

You can customize this variable.