Colourist checks source of red filter (8)
I believe the answer is:
strainer
'filter' is the definition.
(strainer is a kind of filter)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for strainer that I've seen before include "something for tea" , "Person making too much effort" , "riddle?" , "Filtering device" , "One trying very hard" .)
