It counts as a hazard for ramblers (5)
I believe the answer is:
adder
'it counts as a hazard for ramblers' is the definition.
The definition suggests a singular noun which matches the answer.
This is the entire clue.
Can you help me to learn more?
(Other definitions for adder that I've seen before include "Venemous snake" , "Type of snake" , "poisoner" , "Viper common in northern Eurasia" , "Snake (like an abacus?)" .)