Civil liberties or Personal Freedoms, are, as the names suggest, freedoms and rights that are guaranteed to the people by the government. Some examples are: Freedom of press, freedom of speech, freedom of religion, among others.
Depending on what kind of liberties we're talking about, Conservatives are the least likely to support government action to protect civil liberties.
For example, freedom of religion gives all citizens the right to practice any religion or not to practice any, if they don't want to. The majority of Conservatives are Christians, and for this reason, they believe everyone else should be too. So freedom of religion might represent a "threat" to Christians when people choose other religions. This is an example of how Conservatives could be the least likely to support civil liberties.