It will be in most winter sportsmen's kit (3)
I believe the answer is:
ski
This might be a double definition.
'it will be in most winter sportsmen's' is the first definition.
The definition suggests a singular noun which matches the answer.
'kit' is the second definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's an association between them I don't understand?
Can you help me to learn more?
(Other definitions for ski that I've seen before include "Winter sports equipment" , "Pole? How one often ends" , "Use runners crossing snow" , "go uphill? Probably not!" , "Travel across snow" .)