Beat Nathaniel up? (3)
I believe the answer is:
tan
'beat' is the definition.
(tan can mean to beat or hit)
'nathaniel up' is the wordplay.
'nathaniel' becomes 'nat' (I've seen this in other clues).
'up' is a reversal indicator (in down clue: letters go upwards).
'nat' back-to-front is 'TAN'.
(Other definitions for tan that I've seen before include "Turn dark in sun" , "Get the effect of the sun." , "Catch the sun" , "Lie in sun" , "Nice brown induced by sun" .)