a reduced or condensed version of the two common jibes "spaz" and "clarrt", both of which are also shortened forms of insults. Spaz being the shortened version of spastic. Clarrt being the short for of razzclot (razz clot being the Jamaican name forthe chunky part of menstral blood).
Spazzclarrt is used by clever people who are talking to white-wide-boys-who-think-they're-black to take the piss by introducing a clearly stupid new piece of urban vocabulary in the hope it will be used in the presence of some real bad ass mother fucker, thereby causing said wannabe white wide boy to be revealed for the numpty he / she is and leading to their ejection from the group.
"We was rinsin dis mash op rave was gabba innit blod"
Developed in the 20th century, spazclarrt was used to tell cunts from hoxton they should be adminstering the drug ketamine to teenage girls from the scene, blud, geon.
"Ayyy Spazclarrt getter meen? Ya dun know bof dem ketamine, safe bransgore mush."