Discouragement (9)
I believe the answer is:
deterrent
'discouragement' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for deterrent that I've seen before include "Tending to put off" , "Discouragement, disincentive" , "Eg, a nuclear weapon" , "It acts to discourage" , "Something that puts people off" .)