Inside the root directory of your pyrit user there is a .pyrit file. Inside that there is a file called blobspace, inside that there is a essid file and a password file. Simply delete the password file.
kracker@tools ~ $ cd .pyrit/
kracker@tools ~/.pyrit $ ls
kracker@tools ~/.pyrit $ cd blobspace/
kracker@tools ~/.pyrit/blobspace $ ls
kracker@tools ~/.pyrit/blobspace $
The smarter thing to do is to use the attack passthrough mode so you can specify the wordlist each time. Just my 2 cents.