Loose violin section repels composer (4)
I believe the answer is:
ives
'composer' is the definition.
(composer Charles Ives)
'loose violin section repels' is the wordplay.
'section' indicates a hidden word.
'repels' shows that the letters should be reversed in order (I've seen 'repelling' mean this).
'sevi' is hidden within 'loose violin'.
'sevi' written backwards gives 'IVES'.
(Other definitions for ives that I've seen before include "he composed" , "Saint of Cornwall or Cambridgeshire" , "US composer, d. 1954 - US folk singer, d. 1995" , "This classical composer" , "American composer of Three Places in New England, d. 1954" .)