Simple stone surrounded by gold before (7)
I believe the answer is:
austere
'simple' is the definition.
(I've seen this before)
'stone surrounded by gold before' is the wordplay.
'stone' becomes 'st'.
'surrounded by' indicates putting letters inside.
'gold' becomes 'au' (Au is the chemical symbol for gold).
'before' becomes 'ere' (usually literary).
'au'+'ere'='auere'
'st' put within 'auere' is 'AUSTERE'.
(Other definitions for austere that I've seen before include "Stern, grave" , "Serious" , "Grim -- a US tree (anag)" , "Grave, unsmiling" , "severely self-disciplined" .)