Just beat up again (3)
I believe the answer is:
pip
'just beat' is the definition.
'pip' can be an answer for 'beat' (pipping is a kind of beating). I'm unsure of the 'just' bit.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for pip that I've seen before include "Just beat, often at the post" , "'Seed, of an apple say (3)'" , "Narrowly beat" , "Philip" , "Annoyed" .)