Servant goes after farm animal in frenzy (7)
I believe the answer is:
rampage
'frenzy' is the definition.
(I've seen this before)
'servant goes after farm animal' is the wordplay.
'servant' becomes 'page' (a royal servant).
'goes after' is a charade indicator (letters next to each other).
'farm animal' becomes 'ram' (male sheep).
'page' after 'ram' is 'RAMPAGE'.
'in' acts as a link.
(Other definitions for rampage that I've seen before include "Dash around violently" , "Run riot" , "Fury" , "Frenzy" , "Violent rush" .)