Writer keeps first and sixth letter in alias (5)
I believe the answer is:
kafka
'writer' is the definition.
(Kafka is an example)
'keeps first and sixth letter in alias' is the wordplay.
'keeps first' becomes 'k' (1st letter of 'keeps').
'and' says to put letters next to each other.
'sixth letter' becomes 'f' (sixth letter of the alphabet).
'in' is an insertion indicator.
'alias' becomes 'aka' (synonyms).
'f' placed inside 'aka' is 'afka'.
'k'+'afka'='KAFKA'
(Other definitions for kafka that I've seen before include "Franz ---, Trial, Castle author" , "Novelist's" , ""Metamorphosis" author" , "Influential German-speaking existential novelist" , "Franz -, Austrian novelist (The Trial)" .)