Serious English author (6)
I believe the answer is:
sterne
'author' is the definition.
(Laurence Sterne, 1713 - 1768)
'serious english' is the wordplay.
'serious' becomes 'stern' (I've seen this before).
'english' becomes 'e' (abbreviation).
'stern'+'e'='STERNE'
(Other definitions for sterne that I've seen before include "18th-century novelist" , "Author of Tristram Shandy, d. 1768" , "Laurence ..., author of 'Tristram Shandy'" , "Irish-born novelist (A Sentimental Journey)" , "Laurence ...... wrote ` `Tristram Shandy' '" .)