Clue: Man interrupting singer after Tosca's entrance gets tongue-lashing (7-2)
Answer: TALKING-TO
Explanation: Definition: tongue-lashing
 [ KING(man/a piece in chess) **contained in**(interrupting) ALTO(a person with the highest adult male singing voice, or with the lowest female singing voice) ] **placed below**(after, in a down clue) **1st letter of**(…'s entrance) "Tosca".