Suggestion assistant should postpone article (4)
I believe the answer is:
idea
'suggestion' is the definition.
(I've seen this before)
'postpone article' is the wordplay.
'postpone' becomes 'ide' (I can't explain this - if you can you should give a lot more credence to this answer).
'article' becomes 'a' (example of the part-of-speech).
'ide'+'a'='IDEA'
'assistant should' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
(Other definitions for idea that I've seen before include "a wheeze" , "Notion, belief" , "Suggestion" , "Aim" , "It comes to mind" .)