Wave behind track as a precaution (7,7)
I believe the answer is:
circuit breaker
'a precaution' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'wave behind track as' is the wordplay.
'wave' becomes 'breaker' (breaker is a kind of wave).
'behind' means one lot of letters go next to another.
'track as' becomes 'circuit' (synonyms. I am not sure about the 'as' bit.).
'breaker' put after 'circuit' is 'CIRCUIT-BREAKER'.
Can you help me to learn more?
(Other definitions for circuit breaker that I've seen before include "means to detach from current" , "power cut-off" , "may interrupt a signal" , "Electric safety device" .)