tell on in WordNet English dictionary

1. give away information about somebody
   "He told on his classmate who had cheated on the exam"
   denounce  tell on  betray  give away  rat  grass  shit  shop  snitch  stag 
   
2. produce an effect or strain on somebody
   "Each step told on his tired legs"
   tell on 
   

tell on in English Wiktionary