Finally sees instructor demonstrate filter (8)
I believe the answer is:
strainer
'filter' is the definition.
(I know that strainer is a type of filter)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for strainer that I've seen before include "one won't let everything go through" , "who tries really hard?" , "One trying very hard" , "one full of holes" , "Tea leaf remover" .)