Slow mover upsetting to Tories (8)
I believe the answer is:
tortoise
'slow mover' is the definition.
(animal which moves slowly)
'upsetting to tories' is the wordplay.
'upsetting' indicates anagramming the letters.
'to'+'tories'='totories'
'totories' with letters rearranged gives 'TORTOISE'.
(Other definitions for tortoise that I've seen before include "Slow-moving reptile that won race against a hare" , "Slow-moving land reptile" , "One shelled" , "Reptile with a shell" , "Mobile home owner?" .)