I modified using one? Very clever (9)
I believe the answer is:
ingenious
'very clever' is the definition.
(ingenious means very clever)
'i modified using one?' is the wordplay.
'modified' is an anagram indicator.
'using'+'one'='usingone'
'usingone' with letters rearranged gives 'ngenious'.
'i'+'ngenious'='INGENIOUS'
(Other definitions for ingenious that I've seen before include "Creative" , "Displaying art" , "Skilfully contrived" , "Showing inventiveness" , "Artless" .)