Literary drudge and marshal in carriage (7)
I believe the answer is:
hackney
'carriage' is the definition.
(I know that hackney is a type of carriage)
'literary drudge and marshal' is the wordplay.
'literary drudge' becomes 'hack' (I've seen this in another clue).
'and' means one lot of letters go next to another.
'marshal' becomes 'ney' (I've seen this in other clues).
'hack'+'ney'='HACKNEY'
'in' is the link.
(Other definitions for hackney that I've seen before include "Old cab - London borough" , "A kind of taxi or car for hire" , "district of London" , "draught horse" , "Wear out" .)