Smoker may need this to get off the bus (6)
I believe the answer is:
alight
'smoker may need this to get off the bus' is the definition.
'alight' can be an answer for 'to get' (thesaurus). I'm not sure about the remainder of the definition.
'smoker may need this to get off' is the wordplay.
I cannot really understand how this works, but
'get off' could be 'light' (synonyms) and 'light' is present in the answer.
A single letter 'a' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for alight that I've seen before include "Come to rest on the ground" , "Get out of train" , "Brilliant" , "Dismount" , "Descend from vehicle" .)