A taxi passenger’s last to be dropped some way away (4)
'some way away' is the definition.
(afar can mean far away)
'a taxi passenger's last to be dropped' is the wordplay.
'taxi passenger' becomes 'fare' (fare can mean someone paying a taxi fare).
'last to be dropped' means to remove the last letter (the last letter is dropped).
'fare' with its final letter taken off is 'far'.
(Other definitions for afar that I've seen before include "Distant parts", "A long distance away", "Pull out at a distance", "a good way off", "(From/at) a great distance".)