Rocky Mountain resident turning up pickled? That's too much (3)
I believe the answer is:
elk
'rocky mountain resident turning' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'up pickled? that's too much' is the wordplay.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'that's too much' says the answer is hidden in the clue (the clue hides the answer plus unneeded letters).
'kle' is hidden within 'pickled'.
'kle' back-to-front is 'ELK'.
Can you help me to learn more?
(Other definitions for elk that I've seen before include "Moose-like deer" , "Type of moose" , "Asian moose" , "Large deer of N Europe and Asia" , "European moose" .)