Train carriage's rear section withdrawn by engineers (7)
I believe the answer is:
retinue
'train' is the definition.
(people following someone in a procession)
'carriage's rear section withdrawn by engineers' is the wordplay.
I cannot really see how this works, but
'engineers' could be 're' (Royal Engineers) and 're' is present in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for retinue that I've seen before include "Group around VIP" , "Body of followers" , "Suite of followers" , "Body of aides" , "company" .)