Knocking sound thrice at bottom of door, moving to the top (3-1-3)
I believe the answer is:
rat-a-tat
'knocking sound' is the definition.
(I've seen this before)
'thrice at bottom of door moving to the top' is the wordplay.
I cannot really see how this works, but
'at' is found in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for rat-a-tat that I've seen before include "Knocking sound" , "Rapping sound" , "Noise of knocking" .)