More daft (7)
I believe the answer is:
dottier
'more daft' is the definition.
('dotty' can be a synonym of 'daft')
This is the entire clue.
(Other definitions for dottier that I've seen before include "with even less reason" , "less rational" , "Crazier" , "more absurd" , "Detroit (anag) - more eccentric" .)