Animal in mountain pasture, a cat with no tail (6)
I believe the answer is:
alpaca
'animal' is the definition.
(thesaurus)
'mountain pasture a cat with no tail' is the wordplay.
'mountain pasture' becomes 'alp' (I've seen this before).
'with no tail' means to remove the last letter.
'cat' with its last letter taken off is 'ca'.
'alp'+'a'+'ca'='ALPACA'
'in' acts as a link.
(Other definitions for alpaca that I've seen before include "woolly character?" , "Cloth made from wool of S American llama" , "Wool-yielding camelid" , "South American camelid" , "Llama with long silky hair" .)