Vagrant finally failing to find public transport (4)
I believe the answer is:
tram
'public transport' is the definition.
(I've seen this before)
'vagrant finally failing' is the wordplay.
'vagrant' becomes 'tramp' (I've seen this before).
'finally failing' means to remove the last letter.
'tramp' with its final letter removed is 'TRAM'.
'to find' acts as a link.
(Other definitions for tram that I've seen before include "Road vehicle running on tracks" , "Passenger vehicle on rails" , "Public transport vehicle" , "Bus on rails" , "multi-faceted yarn" .)