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 really 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 understand.
This explanation may well be incorrect...
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" .)