Failure left Eros shaken (5)
I believe the answer is:
loser
'failure' is the definition.
(someone who has failed)
'left eros shaken' is the wordplay.
'left' becomes 'l' (common abbreviation).
'shaken' indicates anagramming the letters.
'eros' is an anagram of 'oser'.
'l'+'oser'='LOSER'
(Other definitions for loser that I've seen before include "One who is habitually unsuccessful" , "one that's been left behind" , "Defeated competitor" , "One who regularly fails" , "Person who's a failure" .)