Filter (8)
'filter' is the definition.
(synonyms)
This is all the clue.
(Other definitions for strain that I've seen before include "Mental tension, stress" , "Pass through a sieve" , "Struggle" , "'Stress, tension (6)'" , "Filter the stress" .)
'filter' is the definition.
(strainer is a kind of filter)
This is the entire clue.
(Other definitions for strainer that I've seen before include "Filter, sieve" , "one won't let everything go through" , "Tea leaf remover" , "one full of holes" , "Filtering device" .)