Be a snitch (5)
'be a snitch' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tattle that I've seen before include "'Gossip, idle talk (6)'" , "Tell tales" , "Divulge secrets" , "Inform on someone" , "Gossip, idle chatter" .)
(Other definitions for raton that I've seen before include "Betray" , "Desert" , "Shop" .)