Blow that hurt creates opening (6)
I believe the answer is:
window
'opening' is the definition.
(window is a kind of opening)
'blow that hurt' is the wordplay.
'blow' becomes 'wind'.
'that hurt' becomes 'ow' (exclamation of pain).
'wind'+'ow'='WINDOW'
'creates' is the link.
(Other definitions for window that I've seen before include "Transparent panel of glass" , "One furthest from the aisle?" , "Transparent opening" , "Glazed opening" , "time still available" .)