Decline case of diverse produce (10)
I believe the answer is:
degenerate
'decline' is the definition.
(degenerating is a kind of declining)
'case of diverse produce' is the wordplay.
'case of' says to hollow out the word (remove centre letters) (outsides of).
'produce' becomes 'generate' (generating is a kind of producing**).
'diverse' with its middle taken out is 'de'.
'de'+'generate'='DEGENERATE'
(Other definitions for degenerate that I've seen before include "Rogue" , "Corrupt type" , "Dissolute" , "sink" , "Rake" .)