Small child’s wheeled toy making impact (6)
I believe the answer is:
strike
'impact' is the definition.
(I know that strike is a type of blow)
'small child's wheeled toy' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'child's wheeled toy' becomes 'trike' (tricycle).
's'+'trike'='STRIKE'
'making' acts as a link.
(Other definitions for strike that I've seen before include "Deliver a blow" , "Make a sudden large financial gain" , "Sudden attack; chime" , "Industrial dispute - everybody out" , "An industrial dispute, pickets out" .)