Plod quietly alongside streetcar (5)
I believe the answer is:
tramp
'plod' is the definition.
(I know that plod can be written as tramp)
'quietly alongside streetcar' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'alongside' is a charade indicator (letters next to each other).
'streetcar' becomes 'tram' (synonyms).
'p' put after 'tram' is 'TRAMP'.
(Other definitions for tramp that I've seen before include "Footslog" , "Vagrant, long walk" , "Vagrant, hobo" , "man down on his luck" , "Traveller" .)