Software program, briefly (3)
I believe the answer is:
app
'software program briefly' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for app that I've seen before include "Program for a smart phone, in short" , "Software for mobile devices, in short" , "Software item" , "Software program for a mobile device" , "bit of software" .)