Frightening prospect arming the jerks (9)
I believe the answer is:
nightmare
'frightening prospect' is the definition.
The answer and definition can be both related to thinking as well as being singular nouns.
Maybe there's an association between them I don't understand?
'arming the jerks' is the wordplay.
'jerks' indicates an anagram (I've seen 'jerk' mean this).
'arming'+'the'='armingthe'
'armingthe' is an anagram of 'NIGHTMARE'.
Can you help me to learn more?
(Other definitions for nightmare that I've seen before include "Frightening dream" , "Frightening nocturnal fantasy" , "dreadful experience" , "that might upset the rest" , "Horrible experience" .)