Talkative type to give the game away (10)
There are a few possibilities for this:
tattletale
(Other definitions for snitch that I've seen before include "Steal; inform (on someone)" , "Whistleblower (informal)" , "Inform on someone in slangy way" , "Inform on, tell tales" , "Telltale (sl.)" .)
(Another definition for tattletale that I've seen is " One who may leak".)