Venomous cause of possible dread (5)
I believe the answer is:
adder
'venomous cause' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'possible dread' is the wordplay.
'dread' can be anagrammed to 'ADDER'.
Though, I am not clear how this is indicated.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for adder that I've seen before include "Something you have to reckon with" , "Mathematical reptile" , "British snake; summer" , "Dread (anag)" , "accountant?" .)