Tor is removed from the Ubuntu's version which Trisquel 4.5 is based on.
It think the reason why it was removed from Ubuntu, is because the
package wasn't kept up to date, which is a big security risk for a
program such as Tor. The Tor project advices to use their repository,
so you can receive in much shorter time any fixes they release.
If you are using Trisquel 4.5, the you should follow this guide, as like
you are using Ubuntu 10.10 ("Maverick Meerkat"):
https://www.torproject.org/docs/tor-doc-unix.html
