Following green light turning, hit red light at the back (3,4)
I believe the answer is:
fog lamp
'red light at the back' is the definition.
(light on a vehicle)
'following green light turning hit' is the wordplay.
'following' becomes 'f.' (used when citing page numbers etc).
'green light' becomes 'go' (I've seen this in other clues).
'turning' says the letters should be written backwards.
'hit' becomes 'lamp' (lamp can mean to hit someone).
'go' written backwards gives 'og'.
'f'+'og'+'lamp'='FOG-LAMP'
(Other definitions for fog lamp that I've seen before include "Something that's light" , "Driver's visibility aid in mist" , "It improves visibility" , "Strong car headlight" , "shines amid the gloom" .)