Jar not used by animal as a threat to security (6,5)
I believe the answer is:
trojan horse
'a threat to security' is the definition.
I can't tell whether this definition defines the answer.
'jar not used by animal' is the wordplay.
'used' is an anagram indicator.
'by' says to put letters next to each other.
'animal' becomes 'horse' (type of animal).
'jar'+'not'='jarnot'
'jarnot' anagrammed gives 'trojan'.
'trojan'+'horse'='TROJAN HORSE'
'as' acts as a link.
Can you help me to learn more?
(Other definitions for trojan horse that I've seen before include "Investment aid" , "A trap to be wary of (a wooden one?)" , "Subversive element working for the opposition" , "admitted losing the war" , "the Greeks aggressively piled out of" .)