Rat cleans out family (9)
I believe the answer is:
ancestral
'family' is the definition.
(I've seen this before)
'rat cleans out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'rat'+'cleans'='ratcleans'
'ratcleans' with letters rearranged gives 'ANCESTRAL'.
(Other definitions for ancestral that I've seen before include "Lancaster (anag)" , "from old-timers" , "Patrimonial" , "Relating to one's forebears" , "Inherited from antecedents" .)