About to get brief details (4)
I believe the answer is:
info
'details' is the definition.
(short for information)
'about to get brief' is the wordplay.
'about to get' becomes 'in for' (as in being in for a shock).
'brief' means to remove the last letter (a shorter or briefer version of the word).
'infor' with its final letter taken off is 'INFO'.
(Other definitions for info that I've seen before include "details" , "Data received and understood (abbr)" , "Data (abbrev.)" , "counsel?" , "Gen (abbr)" .)