New train set, handled roughly, is not lasting long (9)
I believe the answer is:
transient
'new train' is the definition.
The answer and definition can be both related to natural events as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'handled roughly is not lasting long' is the wordplay.
I cannot really understand how this works, but
'handled' could be 'ran' (I've seen this in another clue) and 'ran' is found in the answer.
'not' could be 'nt' (synonyms) and 'nt' is present in the answer.
This explanation may well be incorrect...
'set' is the link.
Can you help me to learn more?
(Other definitions for transient that I've seen before include "on the move" , "Lasting a short time" , "Lasting little time" , "Fleeting" , "gone in a trice!" .)