Undercarriage that is stuck on swamp (5)
I believe the answer is:
bogie
'undercarriage' is the definition.
(term for the undercarriage of a train)
'that is stuck on swamp' is the wordplay.
I cannot quite see how this works, but
'swamp' could be 'bog' (both can mean a wet or marshy area) and 'bog' is found in the answer.
'that is' could be 'ie' (short for Latin 'id est', 'that is') and 'ie' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for bogie that I've seen before include "Set of railcoach wheels" , "Freight truck" , "Wheeled undercarriage that supports a rail car" , "Pivoted group of four or six wheels on an engine" , "Part of carriage" .)