Unhide files in your home folder (Ctrl+H) add the following to the bottom of the .bashrc file on a new line:
alias clearmem="sudo sh -c 'echo 3 >/proc/sys/vm/drop_caches'"
Save and close the file. Then type:
source .bashrc
to activate the new alias.
Then every time you want to clear the memory, just type clearmem in a terminal. Lite Tweaks in 3.x does not work in series 2.x The above is a workaround.