Descends from vehicle because it's covering headlamp (7)
I believe the answer is:
alights
'descends' is the definition.
(alighting is a kind of descending)
'because it's covering headlamp' is the wordplay.
'because' becomes 'as' (I've seen this in other clues).
'it's covering' is an insertion indicator.
'headlamp' becomes 'light' (I am not sure about this - if you are sure you should believe this answer much more).
'as' going around 'light' is 'ALIGHTS'.
'from vehicle' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for alights that I've seen before include "Gets down from, bus or train" , "Touches down" , "Comes down or dismounts" , "Disembarks" , "Lands" .)