Prosper - like Dusty Miller? (8)
I believe the answer is:
flourish
'prosper like dusty miller?' is the definition.
'flourish' can be an answer for 'prosper' (synonyms). I am not certain of the 'like dusty miller?' bit.
'prosper like' is the wordplay.
'prosper' becomes 'flour' (I can't explain this - if you can you should give a lot more credence to this answer).
'like' becomes 'ish' (similar in meaning).
'flour'+'ish'='FLOURISH'
(Other definitions for flourish that I've seen before include "Grow vigorously and healthily" , "Bloom" , "success" , "Thrive; ornamental passage of music" , "show off" .)