Control signals malfunctioning if craft comes to Earth (7,6)
I believe the answer is:
Here is my best explanation:
'control signals' is the definition.
'malfunctioning if craft comes to earth' is the subsidiary indication.
'malfunctioning' indicates anagramming the letters.
'comes to earth' becomes 'lights'.
'ifcraft' anagrammed gives 'traffic'.
(Other definitions for traffic lights that I've seen before include "Illuminated road signals", "Road feature" and "Road signals".)