Crazy Greek character climbing — old and free from injury (9)
I believe the answer is:
undamaged
'free from injury' is the definition.
'crazy greek character climbing old' is the wordplay.
'crazy' becomes 'mad' (synonyms).
'greek character' becomes 'nu' (letter from the Greek alphabet).
'climbing' is a reversal indicator (in a down clue, letters climb up).
'old' becomes 'aged' (similar in meaning).
'mad'+'nu'='madnu'
'madnu' in reverse letter order is 'undam'.
'undam'+'aged'='UNDAMAGED'
'and' acts as a link.
(Other definitions for undamaged that I've seen before include "sound" , "without injuries" , "Not harmed or injured" .)