Trudge quietly and behold first ditch (4)
I believe the answer is:
plod
'trudge' is the definition.
('plod' can be a synonym of 'trudge')
'quietly and behold first ditch' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'and' is a charade indicator (letters next to each other).
'behold' becomes 'lo'.
'first' suggests taking the first letters.
The first letter of 'ditch' is 'd'.
'p'+'lo'+'d'='PLOD'
(Other definitions for plod that I've seen before include "Heavy walk; PC (slang)" , "Walk heavily (like a policeman?)" , "Tread wearily" , "Work painstakingly" , "coppers?" .)