Whingers disconcerted US composer (8)
I believe the answer is:
gershwin
'us composer' is the definition.
(I've seen this before)
'whingers disconcerted' is the wordplay.
'disconcerted' is an anagram indicator.
'whingers' is an anagram of 'GERSHWIN'.
(Other definitions for gershwin that I've seen before include "American composer" , "he noted" , "Composer of Rhapsody in Blue, d.1937" , "SECOND PART OF 14" , "George ........ composed ` `Porgy and Bess' '" .)