Dorothy’s brief point (3)
I believe the answer is:
dot
'point' is the definition.
(synonyms)
'dorothy's brief' is the wordplay.
'dorothy's' becomes 'dot's' (nickname for someone called Dorothy).
'brief' means to remove the last letter.
'dots' with its last letter taken off is 'DOT'.
(Other definitions for dot that I've seen before include "Long-ago year?" , "Flyspeck: period in a web address" , "A point, small round mark" , "Full stop, point" , "One of the signals in Morse code" .)