Design detail, for short (4)
I believe the answer is:
spec
'design detail for short' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for spec that I've seen before include "On - means on the chance of achieving something" , "Detailed description of design criteria (abbr)" , "Awkward, clumsy" , "Required standard of workmanship" , "Bet" .)