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 can't understand how one could define the other.
'up pickled? that's too much' is the wordplay.
'up' is a reversal indicator (in down clue: letters go upwards).
'that's too much' indicates the answer is hidden within the clue (the clue hides the answer plus unneeded letters).
'kle' can be found hidden inside '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" .)