Broken (4)
'broken' is the definition.
(bust can mean broken)
This is the entire clue.
(Other definitions for bust that I've seen before include "Head-and-shoulders piece" , "8 across" , "Piece of sculpture - broken!" , "Houdon's Voltaire" , "Small statue" .)
(Other definitions for inoperable that I've seen before include "Not curable by surgery" , "Incapable of being made to work" .)
(Other definitions for arrow that I've seen before include "Direction pointer" , "Narrow missile" , "Direction indicator" , "Cupid's projectile" , "Missile for bowman" .)