Do well in school, stifling angry expression (8)
I believe the answer is:
flourish
'do well' is the definition.
(thesaurus)
'school stifling angry expression' is the wordplay.
'school' becomes 'fish' (group of fishes).
'stifling' is an insertion indicator (some letters get stifled or contained).
'angry expression' becomes 'lour' (I can't explain this - if you can you should give a lot more credence to this answer).
'fish' placed around 'lour' is 'FLOURISH'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for flourish that I've seen before include "Thrive; ornamental passage of music" , "Fine food is hard to" , "Prosper - display" , "Grow vigorously and healthily" , "success" .)