One blessed Green sucker (5)
I believe the answer is:
straw
'sucker' is the definition.
(I've seen this before)
'one blessed green' is the wordplay.
'one blessed' becomes 'st' (abbreviation for saint).
'green' becomes 'raw' (synonyms).
'st'+'raw'='STRAW'
(Other definitions for straw that I've seen before include "Stalk - tube for drinking" , "Dry stalk of grain" , "What a sucker gets given" , "Plant fibre used as fodder" , "Thin tube; yellow" .)