Graham who co-founded The Hollies (4)
I believe the answer is:
nash
'graham who co-founded the hollies' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nash that I've seen before include "John --, British architect" , "Famed English architect" , "Architect of Buckingham Palace, d. 1835" , "John -, English architect, designed Regent's Park" , "John -, Eng. architect" .)