Rotten old pear that may be spotted in forest (7)
I believe the answer is:
leopard
'spotted in forest' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'rotten old pear' is the wordplay.
'rotten' indicates anagramming the letters.
'old'+'pear'='oldpear'
'oldpear' with letters rearranged gives 'LEOPARD'.
'that may be' is the link.
Can you help me to learn more?
(Other definitions for leopard that I've seen before include "Spotted feline" , "Big cat with spots" , "The cat that does not change its spots" , "Panther" , "Large spotted cat" .)