Love to upset small animal (4)
I believe the answer is:
vole
'small animal' is the definition.
'vole' can be an answer for 'animal' (thesaurus). I'm not sure about the 'small' bit.
'love to upset' is the wordplay.
'to upset' indicates anagramming the letters.
'love' is an anagram of 'VOLE'.
Can you help me to learn more?
(Other definitions for vole that I've seen before include "River-bank rodent" , "River bank rodent" , "Small burrowing animal - love it" , "Small mouse-like rodent" , "win all the tricks" .)