PSV stuff needed after the end of treatment (4)
I believe the answer is:
tram
'psv' is the definition.
(public service vehicle)
'stuff needed after the end of treatment' is the wordplay.
'stuff' becomes 'ram' (ramming is a kind of stuffing**).
'needed after' is a charade indicator (letters next to each other).
'the end of' suggests the final letters.
The final letter of 'treatment' is 't'.
'ram' after 't' is 'TRAM'.
(Other definitions for tram that I've seen before include "Road vehicle running on tracks" , "Street vehicle running on rails" , "Electrically driven transport" , "Rail vehicle" , "multi-faceted yarn" .)