Trouble with the carriage at the end of the line (4)
I believe the answer is:
care
'trouble with' is the definition.
'the carriage at the end of the line' is the wordplay.
'the carriage' becomes 'car' (I've seen this in other clues).
'at the end of' says to take the final letters.
The last letter of 'line' is 'e'.
'car'+'e'='CARE'
(Other definitions for care that I've seen before include "Have concern or regard" , "Consideration" , "Serious attention and thought" , "Protective custody" , "Caution; keeping" .)