Hit on a nerd for a change (4-3)
I believe the answer is:
rear-end
'hit' is the definition.
(I know that rear-end is a more specific form of the action hit)
'on a nerd for a change' is the wordplay.
'on' becomes 're' ('on' can be mean 'with reference to').
'for a change' indicates anagramming the letters.
'nerd' with letters rearranged gives 'rend'.
're'+'a'+'rend'='REAR-END'
(Other definitions for rear-end that I've seen before include "Crash into back of another vehicle" , "Crash into another vehicle from behind (US)" , "hit a vehicle" .)