Animal disease causes amazement (8)
I believe the answer is:
staggers
'causes amazement' is the definition.
(I've seen this before)
'animal disease' is the wordplay.
I cannot quite see how this works, but
'animal' could be 'stag' (stag is a kind of animal) and 'stag' is found within the answer.
The remaining letters 'gers' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for staggers that I've seen before include "Disease affecting farmyard animals" , "is astonishing" , "Form of vertigo" , "Reels and nearly falls" , "astounds" .)