One new expert has nothing clever (9)
I believe the answer is:
ingenious
'clever' is the definition.
('ingenious' can be a synonym of 'clever')
'one new expert has nothing' is the wordplay.
'one new' becomes 'in' (I've seen this in other clues).
'expert' becomes 'genius' (genius is a kind of expert**).
'has' means one lot of letters goes inside another.
'nothing' becomes 'o' (looks like zero - 0).
'genius' placed around 'o' is 'genious'.
'in'+'genious'='INGENIOUS'
(Other definitions for ingenious that I've seen before include "Artless" , "Creative" , "Displaying art" , "Showing inventiveness" , "Resourceful" .)