Clue: Donuts regularly consumed by South American composer (5)
Answer: SOUSA
Explanation: Donuts regularly consumed by South American composer (5)
(d)**O**(n)**U**(t)**S** [regularly] *consumed by* **S.A**. (South American) 
*John Philip Sousa (1854-1932) was an American composer, noted for his marches, who helped to develop the sousaphone.