Nice ruse turns out to be unsafe (8)
I believe the answer is:
insecure
'be unsafe' is the definition.
(associated in meaning)
'nice ruse turns out' is the wordplay.
'turns out' indicates an anagram.
'nice'+'ruse'='niceruse'
'niceruse' is an anagram of 'INSECURE'.
'to' acts as a link.
(Other definitions for insecure that I've seen before include "(Feeling) unsafe" , "Not safe or confident in oneself" , "open to attack" , "Defenceless" , "Not adequately protected" .)