Aggressive behaviour Proust periodically exhibited (3)
I believe the answer is:
rut
'aggressive behaviour' is the definition.
'rut' can be an answer for 'behaviour' (I have seen 'Routine behaviour ' mean 'rut' so perhaps 'behaviour' could also mean 'rut'). I'm not certain of the 'aggressive' bit.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for rut that I've seen before include "Grove you should not remain in" , "Furrow left by wheel" , "Kind of groove or fixed habit" , "Oestrus" , "A deep track - get out of it" .)