Clue: 17 man stops breaking off to do nothing (3,4,2,4)
Answer: THE FOOD OF LOVE
Explanation: Definition: 17
An envelope ('stops') of HE ('man') in TFOODOF, an anagram ('breaking') of 'off to do' plus LOVE ('nothing'). The definition '17' MUSIC refers to the famous quotation from Twelfth Night, continued in 12A: If music be the food of love, play on