Clear rants about guardian (11)
I believe the answer is:
transparent
'clear' is the definition.
(similar in meaning)
'rants about guardian' is the wordplay.
'about' indicates anagramming the letters.
'guardian' becomes 'parent' ().
'rants' is an anagram of 'trans'.
'trans'+'parent'='TRANSPARENT'
(Other definitions for transparent that I've seen before include "poor at lying" , "See-through - easily understood" , "Open" , "Lucid - evident - clear" , "Obvious - ingenuous" .)