Fay set off wanting security (6)
I believe the answer is:
safety
'security' is the definition.
(being secure is being safe)
'fay set off' is the wordplay.
'off' is an anagram indicator.
'fay'+'set'='fayset'
'fayset' with letters rearranged gives 'SAFETY'.
'wanting' is the link.
(Other definitions for safety that I've seen before include "State of security" , "The condition of being protected from danger" , "Security; sanctuary" , "Motto of the cautious!" , "Opposite of danger" .)