An upright and stylishly true character (6)
I believe the answer is:
nature
'character' is the definition.
(I've seen this before)
'an upright and stylishly true' is the wordplay.
'upright' says the letters should be written backwards (in a down clue, letters go up).
'and' means one lot of letters go next to another.
'stylishly' indicates anagramming the letters (I've seen this in other clues).
'an' back-to-front is 'na'.
'true' anagrammed gives 'ture'.
'na'+'ture'='NATURE'
(Other definitions for nature that I've seen before include "Fundamental character" , "Basic character" , "Innate quality" , "Disposition; temper" , "sort of reserve" .)