Steel affected by bad weather (5)
I believe the answer is:
sleet
'bad weather' is the definition.
(I've seen this in another clue)
'steel affected' is the wordplay.
'affected' is an anagram indicator.
'steel' with letters rearranged gives 'SLEET'.
'by' is the link.
(Other definitions for sleet that I've seen before include "Partly frozen rain" , "Partially frozen rain" , "Icy rain" , "Rain/ice mix" , "Partly melted falling 16 across or 18 down" .)