Impact, by the sound of it, reversed in experimental psychology (5)
I believe the answer is:
splat
'impact by the sound of it' is the definition.
(sound of something's impact as it hits a surface)
'reversed in experimental psychology' is the wordplay.
'reversed' shows that the letters should be reversed in order.
'in' indicates the answer is hidden within the clue.
'talps' is hidden within 'experimental psychology'.
'talps' in reverse letter order is 'SPLAT'.
(Other definitions for splat that I've seen before include "Noise on landing" , "Piece of wood in a chair back" , "Sound of a soft, wet object striking a surface" , "Noise of soft wet impact; part of a chair back" , "Sound of a wet and squishy impact" .)