Frown on goods starting to be inferior (6)
I believe the answer is:
glower
'frown' is the definition.
(synonyms)
'on goods starting to be inferior' is the wordplay.
'on' is a charade indicator (letters next to each other).
'starting' says to take the initial letters.
'to be inferior' becomes 'lower' ('lower' can be a synonym of 'inferior').
The first letter of 'goods' is 'g'.
'g' put next to 'lower' is 'GLOWER'.
(Other definitions for glower that I've seen before include "Stare fiercely" , "Angry stare" , "Threatening look" , "Fierce look" , "Look thunderous" .)