Person being questioned there did see punch thrown (7,3)
I believe the answer is:
witness box
'person' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'questioned there did see punch thrown' is the wordplay.
I cannot quite understand how this works, but
'see' could be 'witness' (to witness something is to see it happen) and 'witness' is found in the answer.
'punch' could be 'box' (I've seen this before) and 'box' is found in the answer.
No letters remain.
This explanation may well be incorrect...
'being' acts as a link.
Can you help me to learn more?
(Other definitions for witness box that I've seen before include "Place for giving evidence" , "From where one testifies" , "Courtroom enclosure" .)