Aged fool definitely has it (3)
I believe the answer is:
old
'aged' is the definition.
(similar in meaning)
'fool definitely has it' is the wordplay.
'has it' indicates a hidden word.
'OLD' is hidden in the letters of 'fool definitely'.
(Other definitions for old that I've seen before include "out of the ark" , "SECOND PART OF 14" , "Long in the tooth" , "Wild clematis" , "Former, previous" .)