Ranted about being passionate (6)
I believe the answer is:
ardent
'passionate' is the definition.
(similar in meaning)
'ranted about' is the wordplay.
'about' indicates anagramming the letters.
'ranted' anagrammed gives 'ARDENT'.
'being' is the link.
(Other definitions for ardent that I've seen before include "Burning, passionate" , "Loving and fiery" , "Ranted, being impassioned" , "Passionate, fervent" , "Fiery and zealous" .)