Sometimes called, for short (3)
I believe the answer is:
aka
'sometimes called for short' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for aka that I've seen before include "Notation indicating alias or other name" , "Notation with initials indicating alternative name" , "Also known as, initially" , "Using the byline" , "Notation indicating alternative identity" .)