So worried about grim aromas (6)
I believe the answer is:
odours
'aromas' is the definition.
('odour' can be a synonym of 'aroma')
'so worried about grim' is the wordplay.
'worried' indicates anagramming the letters.
'about' is an insertion indicator.
'grim' becomes 'dour' ('dour' can be a synonym of 'grim').
'so' anagrammed gives 'os'.
'os' placed around 'dour' is 'ODOURS'.
(Other definitions for odours that I've seen before include "for the nose to detect" , "Smells, good or bad" , "Smells, redolences" , "Aromas, pungencies" , "bouquets" .)