In time, beat up relative (6)
I believe the answer is:
agnate
'relative' is the definition.
(agnate is a kind of relative)
'in time beat up' is the wordplay.
'in' is an insertion indicator.
'time' becomes 'age' (age is a kind of time).
'beat' becomes 'tan' (I've seen this before**).
'up' is a reversal indicator (in down clue: letters go upwards).
'tan' back-to-front is 'nat'.
'age' going around 'nat' is 'AGNATE'.
(Other definitions for agnate that I've seen before include "Related through male descent on father's side (6)" , "Descended from the same male ancestor" , "Relative" , "Get an A (anag.)" .)