Crosby, Stills, ___ & Young (4)
I believe the answer is:
nash
(Other definitions for nash that I've seen before include "John -, Eng. architect" , "Famous dandy, Beau --" , "English architect, d. 1835 - American poet, d. 1971" , "John -, English architect, designed Regent's Park" , "Uncontrollable emotion" .)