Inferior work accepted by railway (4)
I believe the answer is:
Here is my best explanation:
'inferior' is the definition.
('ropy' can be similar in meaning to 'inferior')
'work accepted by railway' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'accepted by' is an insertion indicator.
'railway' becomes 'ry' (abbreviation for railway).
'op' put inside 'ry' is 'ROPY'.