Fir cone source (7)
I believe the answer is:
conifer
'source' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'fir cone' is the wordplay.
'fir cone' can be anagrammed to 'CONIFER'.
However, I'm not sure how the anagram is indicated.
Can you help me to learn more?
(Other definitions for conifer that I've seen before include "In force (anag.)" , "Tree such as pine, yew etc" , "Fir or pine, for example" , "Evergreen tree" , "The tree keeps its leaves" .)