Regard flat just over the bridge (3-5)
I believe the answer is:
eye-level
'just over the bridge' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'regard flat' is the wordplay.
'regard' becomes 'eye' (I've seen this before).
'flat' becomes 'level' (synonyms).
'eye'+'level'='EYE-LEVEL'
Can you help me to learn more?
(Other definitions for eye-level that I've seen before include "Viewable horizontally" , "The same height as the observer" , "Height at which one sees" , "Head height" , "At one's height of looking" .)