At the point of time in question (4)
I believe the answer is:
then
'time in question' is the definition.
The definition and answer can be both related to time as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'at the point' is the wordplay.
'at' says to put letters next to each other.
'point' becomes 'n' (N is an example).
'the'+'n' is 'THEN'.
'of' is the link.
Can you help me to learn more?
(Other definitions for then that I've seen before include "Consequently" , "soon?" , "Afterwards - as a result" , "Subsequently - previously" , "Once upon a time" .)