Being a failure left Rose in a mess (5)
I believe the answer is:
loser
'being a failure' is the definition.
(I've seen this before)
'left rose in a mess' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in a mess' indicates anagramming the letters.
'rose' is an anagram of 'oser'.
'l'+'oser'='LOSER'
(Other definitions for loser that I've seen before include "No-hoper" , "Ineffectual person who regularly fails" , "Person who's a failure" , "Washout" , "lemon" .)