Content of family tree is wrong, as it happens (4-4)
I believe the answer is:
real-time
'as it happens' is the definition.
(I've seen this in another clue)
'content of family tree is wrong' is the wordplay.
'content of' indicates the central letters.
'is wrong' indicates anagramming the letters.
The middle letters of 'family' are 'amil'.
'amil'+'tree'='amiltree'
'amiltree' with letters rearranged gives 'REAL-TIME'.
(Other definitions for real-time that I've seen before include "Of computer system, responding instantly to input data" , "Style of computing" , "Fast-acting mode of computing" , "Of computer system, able to respond immediately to input" .)