Family lent a car's running wild (9)
I believe the answer is:
ancestral
'family' is the definition.
(I've seen this before)
'lent a car's running wild' is the wordplay.
'running wild' indicates an anagram.
'lent'+'a'+'cars'='lentacars'
'lentacars' anagrammed gives 'ANCESTRAL'.
(Other definitions for ancestral that I've seen before include "Patrimonial" , "Belonging to the house" , "from old-timers" , "Relating to one's forebears" , "To do with forebears, say stately home" .)