Writer whose hair style could be any (6)
I believe the answer is:
bunyan
'writer' is the definition.
(John Bunyan)
'hair style could be any' is the wordplay.
'hair style' becomes 'bun' (I've seen this in another clue).
'could be' is an anagram indicator.
'any' is an anagram of 'yan'.
'bun'+'yan'='BUNYAN'
'whose' acts as a link.
(Other definitions for bunyan that I've seen before include "John . . . . . . wrote 'The Pilgrim's Progress'" , "John ... wrote 'The Pilgrim's Progres'" , "The Pilgrim's Progress author, d. 1688" , "Writer" , "author John" .)