Reduction in blue-green colour makes water browner (3)
I believe the answer is:
tea
'colour makes water browner' is the definition.
I can't judge whether this defines the answer.
'reduction in blue-green' is the wordplay.
'reduction in' means to remove the last letter (the number of letters in the word is reduced).
'blue green' becomes 'teal' (I've seen this in another clue).
'teal' with its final letter taken away is 'TEA'.
Can you help me to learn more?
(Other definitions for tea that I've seen before include "Eg, gunpowder, pekoe" , "tips for the cup?" , "Common drink" , "For Japanese ceremony" , "Tisane" .)