Student, in a period of prosperity, is flowering (6)
I believe the answer is:
abloom
'is flowering' is the definition.
('abloom' can be a synonym of 'flowering')
'student in a period of prosperity' is the wordplay.
'student' becomes 'l' (as in L-plates for learner drivers).
'in' is an insertion indicator.
'period of prosperity' becomes 'boom' (I've seen this before).
'a'+'boom'='aboom'
'l' placed within 'aboom' is 'ABLOOM'.
(Other definitions for abloom that I've seen before include "covered in flowers?" , "full of colour" , "Flowering" , "In flower" , "Flourishing" .)