Sieve, filter (4)
I believe the answer is:
sift
This clue is a double definition.
'sieve' is the first definition.
(I know that sieve can be written as sift)
'filter' is the second definition.
(as in sifting through something)
(Other definitions for sift that I've seen before include "Analyse carefully in fist" , "Get lumps from (flour)" , "Filter, riddle" , "Remove lumps from, eg, flour" , "Use a sieve" .)