Old Inca ten confused (7)
I believe the answer is:
ancient
'old' is the definition.
(similar in meaning)
'inca ten confused' is the wordplay.
'confused' indicates anagramming the letters.
'inca'+'ten'='incaten'
'incaten' with letters rearranged gives 'ANCIENT'.
(Other definitions for ancient that I've seen before include "Extremely old" , "from Aristophanes' time" , "showing signs of wear?" , "Shakespearean standard-bearer" , "Veteran" .)