Brief expression not long-lasting (5-4)

I believe the answer is:

short-term

'not long-lasting' is the definition.
(I've seen this before)

'brief expression' is the wordplay.
'brief' becomes 'short' (synonyms).
'expression' becomes 'term' (I've seen this before).
'short'+'term'='SHORT-TERM'

(Other definitions for short-term that I've seen before include "Concerned only with the immediate future" , "Not concerned with long timescales" , "Not lasting long" , "Temporary" , "Not long-lasting" .)

I've seen this clue in the Sydney Morning Herald.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.