Tree sap forced out (3)
I believe the answer is:
asp
'forced out' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'tree sap' is the wordplay.
'sap' can be anagrammed to 'ASP'.
But, I am not sure how this is indicated.
Can you help me to learn more?
(Other definitions for asp that I've seen before include "It proved deadly for Cleopatra" , "the snake in Cleopatra''s bosom" , "Snake found in spa" , "One secreting poison" , "Small poisonous snake" .)