There are two parts...1. Having the right access level and 2. Having a need to see it.
Having a TS does not mean you can look at all TS documents, you still need a reason.
You are correct. You should also know that once toy have been granted a Security Clearance, while it can be 'revoked', it is usually valid for a certain number of years before it has to be renewed.
HAVING A SECURITY CLEARANCE, as you pointed out, is still not reason to have ACCESS to classified.
Brennan is no longer Director of the CIA. He does not work in an official capacity for the US Government; therefore, he no longer has a legal 'NEED TO KNOW'.
(Once Hillary Clinton stepped down from being Secretary of State and left the employment of the Federal Government she maintained a valid Security clearance, but she no longer had a legal 'need to know' and therefore no longer had the need for access to classified....ESPECIALLY TOP SECRET READ-IN CLASSIFIED DATA, which was found on her server. When you are 'read-out' of a program you are briefed you will never talk about that program again and have no access to data involving that information...and you sign a document acknowledging that. The fact that such data was in Hillary's possession, on her server, & in her e-mails was evidence of her having broken those laws regarding the handling of classified.")
ALSO, since Brennan has been proven to have committed Perjury under oath before Congress his security clearance should have been revoked by now. Prosecution is not required to have your security clearance revoked. If an investigation is conducted and you are found to have violated rules, regs, laws, jeopardized national security, engaged in questionable acts, etc... you security clearance can be revoked.
Brennan should not have one today.