Spartan saint seen in gold before (7)
I believe the answer is:
austere
'spartan' is the definition.
('austere' can be a synonym of 'spartan')
'saint seen in gold before' is the wordplay.
'saint' becomes 'st'.
'seen in' indicates putting letters inside.
'gold' becomes 'au' (Au is the chemical symbol for gold).
'before' becomes 'ere' (usually literary).
'au'+'ere'='auere'
'st' going into 'auere' is 'AUSTERE'.
(Other definitions for austere that I've seen before include "Severe or strict in attitude" , "Severe in manner" , "severely self-disciplined" , "Stark" , "Stern, severe" .)