Opening with light blow that hurts! (6)
I believe the answer is:
window
'opening' is the definition.
(a window is an opening)
'with light blow that hurts' is the wordplay.
'with' means one lot of letters go next to another.
'light blow' becomes 'wind' (I am not sure about the 'light' bit.).
'that hurts' becomes 'ow!'.
'wind' put next to 'ow' is 'WINDOW'.
Can you help me to learn more?
(Other definitions for window that I've seen before include "Shop display area" , "Opening to admit light" , "Opening (of opportunity?)" , "Interval for action" , "Skylight" .)