Proposal some decide against (4)
I believe the answer is:
idea
'proposal' is the definition.
(idea can mean a proposal or suggestion)
'some decide against' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'IDEA' is hidden in the letters of 'decide against'.
(Other definitions for idea that I've seen before include "Product of the mind" , "Sudden inspiration?" , "Proposal" , "Thought; concept" , "Notion, image" .)