Marathon run cut short with 1D frequently lacking kit for colder weather (4,5)
I believe the answer is:
long johns
'1d frequently lacking kit for colder weather' is the definition.
I can't judge whether this defines the answer.
'marathon run cut short' is the wordplay.
'marathon' becomes 'long' (marathon can mean long or lengthy).
'run cut short' becomes 'johns' (I can't justify this - if you can you should believe this answer much more).
'long'+'johns'='LONG JOHNS'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for long johns that I've seen before include "warm clothing" , "So-called pirate's" , "Old habits" , "Warm underwear" , "Thermal underpants" .)