No criterion for what a danger signal should be (7,2,2,2)
I believe the answer is:
nothing to go on
'no criterion for what a danger signal should be' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'no criterion for what a danger signal should be' is the wordplay.
I cannot quite see how this works, but
'no' could be 'nothing' (synonyms) and 'nothing' is present in the answer.
'for' could be 'to' (eg both can mean 'in the opinion of') and 'to' is located in the answer.
'be' could be 'go' (going is a kind of being) and 'go' is found in the answer.
The remaining letters 'on' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?