Brown looks awfully good in something green (5)
I believe the answer is:
sepia
'brown' is the definition.
(sepia is a kind of brown)
'looks awfully good in something green' is the wordplay.
I cannot quite see how this works, but
'good' could be 'pi' (I've seen this in other clues) and 'pi' is located in the answer.
'green' could be 'sea' (sea green is a kind of green) and 'sea' is present in the leftover letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sepia that I've seen before include "Rich reddish-brown colour" , "Old drawing" , "Brown of old photos" , "Colour from cuttlefish ink" , "Reddish brown -- ie sap (anag)" .)