Pull up floors, allowing in Charlie's piledriver (4)
I believe the answer is:
Here is my best explanation:
'piledriver' is the definition.
(both can mean a hit in a fight)
'pull up floors allowing in charlie's' is the wordplay.
'pull up' is a reversal indicator (I've seen 'pulled up' mean this).
'floors' becomes 'kos' (to KO is to knock out in boxing).
'allowing in' is an insertion indicator.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'kos' going around 'c' is 'kcos'.
'kcos' in reverse letter order is 'SOCK'.
(Other definitions for sock that I've seen before include "Clothing; punch", "strike", "Strike, hose", "Hit with a powerful blow", "hit", "Very short stocking?", "Foot garment", "component of Christmas present", "Hit forcefully; footwear" and "Covering for the foot".)