Fixed trouble in elevated study (6)
I believe the answer is:
nailed
'fixed' is the definition.
(I've seen this before)
'trouble in elevated study' is the wordplay.
'trouble' becomes 'ail' (synonyms).
'in' is an insertion indicator.
'elevated' says the letters should be written backwards (in a down clue, letters go up).
'study' becomes 'den' (term for a study or office).
'den' written backwards gives 'ned'.
'ail' placed into 'ned' is 'NAILED'.
(Other definitions for nailed that I've seen before include "Properly fixed" , "Fastened with spike" , "Fixed; lead in (anag.)" , "Fastened with metal pin" , "Fastened by Daniel" .)