Clue: One composer surprisingly able, another satisfactory (4,6)
Answer: BELA BARTOK
Explanation: Definition: composer
***(able)** + (Lionel) **BART** ("another" composer) + **O.K.** ("satisfactory") 
*Bela Bartok (1881 – 1945) was a Hungarian composer, while Lionel Bart (1930-1999) wrote "Oliver!", the 1960 musical.