Writer turns in one's biro (5)
I believe the answer is:
ibsen
'writer' is the definition.
(Ibsen is an example)
'turns in one's biro' is the wordplay.
'turns' shows that the letters should be reversed in order.
'in' says the answer is hidden in the clue.
'nesbi' is hidden within 'ones biro'.
'nesbi' backwards is 'IBSEN'.
(Other definitions for ibsen that I've seen before include "Norwegian playwright, d. 1906" , "Norwegian dramatist of 'Hedda Gabler'" , "foreign author" , "Scandinavian playwright" , "Norwegian dramatist, Henrik (1828-1906)" .)