Clever to be elected, then reject negative promises (9)
I believe the answer is:
ingenious
'clever' is the definition.
(I know that clever can be written as ingenious)
'elected then reject negative promises' is the wordplay.
'elected' becomes 'in' (in government).
'then' means one lot of letters go next to another.
'reject' shows that the letters should be reversed in order.
'negative' becomes 'neg' (short for photographic negative).
'promises' becomes 'IOUs' (promises to pay a debt).
'neg' back-to-front is 'gen'.
'in'+'gen'+'ious'='INGENIOUS'
'to be' is the link.
(Other definitions for ingenious that I've seen before include "Brilliant" , "Displaying art" , "Artless" , "Clever, inventive" , "Skilfully contrived" .)