Yearn to find expression that's not a flash in the pan (4,4)
I believe the answer is:
long term
'not a flash in the pan' is the definition.
I can't tell whether this definition defines the answer.
'yearn to find expression' is the wordplay.
'yearn' becomes 'long-' (synonyms).
'to find' is a charade indicator (letters next to each other).
'expression' becomes 'term' (I've seen this in other clues).
'long'+'term'='LONG-TERM'
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for long term that I've seen before include "teachers may find exhausting" , "Such future planning" .)