Badly thought out (3-10)
I believe the answer is:
ill-considered
'badly thought out' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ill-considered that I've seen before include "End collier I/Ds? (anag)" , "Foolish" , "Badly thought out" , "Not carefully planned" , "Rash" .)