high off of marijuana. being clapped is being high, so when you are in this state, usually when you are particularly high, you are clippety clapped.
you may also hear people say "blippety blapped" or "blippety blapped off the blea" or "blippety blapped off the bean"
"bro, could u even believe how shmacked we were last nite"
"yo this is a truth bro, we were clippety clapped of the blea"