Interpret rants, terribly overdue (9)
I believe the answer is:
translate
'interpret' is the definition.
(synonyms)
'rants terribly overdue' is the wordplay.
'terribly' is an anagram indicator.
'overdue' becomes 'late' (similar in meaning).
'rants' anagrammed gives 'trans'.
'trans'+'late'='TRANSLATE'
(Other definitions for translate that I've seen before include "make comprehensible" , "Restate in another language" , "Convert" , "Explain" , "Put into another language" .)