Defend author sheltering dishonourable fellow (9)
I believe the answer is:
barricade
'defend' is the definition.
(I've seen this before)
'author sheltering dishonourable fellow' is the wordplay.
'author' becomes 'barrie' (I've seen this before).
'sheltering' indicates putting letters inside.
'dishonourable fellow' becomes 'cad' (cad can mean a dishonourable person).
'barrie' placed around 'cad' is 'BARRICADE'.
(Other definitions for barricade that I've seen before include "Temporary blockage to obstruct movement" , "Fortification, barrier" , "Obstacle" , "Defend" , "Blockade" .)