The answer is simple and straight-forward:
Having clickjacking protection only on the login page only protects the login page. The rest of your site is still vulnerable
It sounds like you have a bit of a misunderstanding, and are hoping that because the login page is clickjacking-protected, someone can't use clickjacking to attack your site. Unfortunately that is not the case. Clickjacking (typically) relies upon using the credentials of an already-logged in user. As a result, there is no need to target the login page with clickjacking. Rather, you target any other page that has a sensitive action.
In fact, the login page is probably low on the list of pages that need clickjacking protection. The reason is because you can't use clickjacking to enter a password, nor would an attacker know the user's password to log them in even if it was possible. It might be possible to use clickjacking on a login page to login a user if the browser stores the password and suggests it automatically, and then follow that up with a clickjacking attack on another action on the site, therefore building up an exploit from multiple clickjacking attacks. In general though, using clickjacking against a login page is probably not an interesting target in-and-of itself.
As a result, you pretty much have things backward: if you had everything but your login page protected from clickjacking, you'd probably be fine. If you only have your login page protected from clickjacking, then your clickjacking protection is useless.
