Short test covering four details (6)
I believe the answer is:
trivia
'details' is the definition.
(I've seen this before)
'short test covering four' is the wordplay.
'short' means to remove the last letter.
'test' becomes 'trial' ('trial' can be a synonym of 'test').
'covering' means one lot of letters goes inside another.
'four' becomes 'iv' ('IV' can be a synonym of 'four').
'trial' with its last letter removed is 'tria'.
'tria' going around 'iv' is 'TRIVIA'.
(Other definitions for trivia that I've seen before include "Trifles, unimportant details" , "minor points of interest?" , "petty considerations" , "Useless facts" , "Minutiae" .)