Separate the grain from almost three, quietly (6)
I believe the answer is:
thresh
'separate the grain' is the definition.
'thresh' can be an answer for 'separate' (thesaurus). I am unsure of the 'the grain' bit.
'almost three quietly' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'quietly' becomes 'sh'.
'three' with its final letter taken away is 'thre'.
'thre'+'sh'='THRESH'
'from' is the link.
Can you help me to learn more?
(Other definitions for thresh that I've seen before include "Separate grain with flail" , "Separate corn from husks by beating" , "Separate grain from (eg, corn)" , "Separate seed from grain" , "Scots rush" .)