Pick up omen from hatemonger (6)
I believe the answer is:
gather
'pick' is the definition.
(thesaurus)
'up omen from hatemonger' is the wordplay.
'up' indicates an anagram.
'from' indicates named letters should be taken away.
'hatemonger' with 'omen' removed is 'hatger'.
'hatger' anagrammed gives 'GATHER'.
(Other definitions for gather that I've seen before include "make a deduction" , "Collect or asemble" , "Collect or come together" , "The rag (anag.)" , "Convene" .)