Queen's looking up 'brown pigment' (6)
I believe the answer is:
sienna
'brown pigment' is the definition.
(I've seen this in another clue)
'queen's looking up' is the wordplay.
'queen' becomes 'anne' (Queen Anne, i8th-century queen).
'looking' becomes 'is' (I can't justify this - if you can you should believe this answer much more).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'anne'+'is'='anneis'
'anneis' back-to-front is 'SIENNA'.
Can you help me to learn more?
(Other definitions for sienna that I've seen before include "Yellow-brown clay used in paint pigments" , "Italian city and brownish pigment" , "Brownish-yellow colour" , "yellowy-brown" , "reddish brown" .)