Everyone has an outward display of no great depth (7)
I believe the answer is:
shallow
'of no great depth' is the definition.
(I've seen this before)
'everyone has an outward display' is the wordplay.
I cannot quite understand how this works, but
'everyone' could be 'all' (all people) and 'all' is found within the answer.
'display' could be 'show' (synonyms) and 'show' is located in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for shallow that I've seen before include "Trivial" , "Superficial" , "incapable of serious thought" , "Not profound" , "Without depth" .)