Keen to renovate joint (4)
I believe the answer is:
knee
'joint' is the definition.
(I know that knee is a type of joint)
'keen to renovate' is the wordplay.
'to renovate' is an anagram indicator (I've seen 'renovated' mean this).
'keen' anagrammed gives 'KNEE'.
(Other definitions for knee that I've seen before include "Leg bender" , "Joint protected by the patella" , "Technical name for this joint is genu" , "Joint of the body" , "Leg hinge" .)