Five ranted about being green (7)
I believe the answer is:
verdant
'being green' is the definition.
(thesaurus)
'five ranted about' is the wordplay.
'five' becomes 'v' (roman numeral).
'about' indicates anagramming the letters.
'ranted' is an anagram of 'erdant'.
'v'+'erdant'='VERDANT'
(Other definitions for verdant that I've seen before include "Leafy" , "Covered with lush green grass or vegetation" , "Unsophisticated" , "Rather green" , "Having green growth" .)