Nearly half a meal taken by the majority (6)
I believe the answer is:
almost
'nearly' is the definition.
(synonyms)
'half a meal taken by the majority' is the wordplay.
'half a' indicates taking half.
'taken by' says to put letters next to each other.
'the majority' becomes 'most' (most of a group).
'meal' cut in half is 'al'.
'al'+'most'='ALMOST'
(Other definitions for almost that I've seen before include "Nearly, not quite" , "Virtually" , "As good as" , "Well-nigh" , "Not entirely" .)