Row about large impact noise (5)
I believe the answer is:
splat
'impact noise' is the definition.
(the sound of something impacting a surface)
'row about large' is the wordplay.
'row' becomes 'spat' (spat is a kind of row).
'about' means one lot of letters goes inside another.
'large' becomes 'l'.
'spat' going around 'l' is 'SPLAT'.
(Other definitions for splat that I've seen before include "Noise of soft wet impact; part of a chair back" , "Noise on landing" , "amusing noise" , "Sound of a soft, wet object striking a surface" , "Sound of a wet and squishy impact" .)