Under pressure formerly, are United level? (7)
I believe the answer is:
plateau
'level?' is the definition.
(thesaurus)
'under pressure formerly are united' is the wordplay.
'under' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'pressure' becomes 'p' (scientific abbreviation).
'formerly' becomes 'late' (I've seen this in other clues).
'are' becomes 'a' (short for 'are', historical unit of measurement).
'united' becomes 'U' (as in Man U, Manchester United).
'p' put next to 'late' is 'plate'.
'plate'+'a'+'u'='PLATEAU'
(Other definitions for plateau that I've seen before include "tray that is ornamented" , "Level outcrop of land" , "Area of livel high ground" , "relatively flat territory" , "High plain" .)