Snowy step perhaps is small and cold, children step on it first (7)
I believe the answer is:
scrunch
'it first' is the definition.
The definition suggests a singular noun which matches the answer.
'snowy step perhaps is small and cold children step' is the wordplay.
I cannot really see how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is present in the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is located in the answer.
'cold' could be 'c' (eg on taps) and 'c' is found within the answer.
'children' could be 'ch' (genealogical abbreviation) and 'ch' is found within the answer.
This may be the basis of clue (or it may be nonsense).
'on' acts as a link.
Can you help me to learn more?
(Other definitions for scrunch that I've seen before include "Crumple" , "Make a crushing noise" , "Crush, squeeze" , "Loud noise of crushing" , "Sound of packing snow, say" .)