Sick? And hence improved! (8)
I believe the answer is:
enhanced
'improved' is the definition.
(enhancing is a kind of improving)
'sick? and hence' is the wordplay.
'sick?' indicates anagramming the letters (I've seen 'sick' mean this).
'and'+'hence'='andhence'
'andhence' with letters rearranged gives 'ENHANCED'.
(Other definitions for enhanced that I've seen before include "Extended" , "Heightened" , "Increased number" , "Increased in value or quality" , "Improved in quality" .)