Cold became less severe and came to an end (6)
I believe the answer is:
ceased
'came to an end' is the definition.
('cease' can be a synonym of 'come to an end')
'cold became less' is the wordplay.
'cold' becomes 'C' (eg on taps).
'became less' becomes 'eased' (to ease or ease off can mean to decrease).
'c'+'eased'='CEASED'
'severe and' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for ceased that I've seen before include "Came to a close" , "Stopped or discontinued" , "Concluded" , "Finished" , "Terminated" .)