Plan for assistant from top to bottom (4)
I believe the answer is:
idea
'plan' is the definition.
(I've seen this in another clue)
'for assistant from top to bottom' is the wordplay.
'for assistant' becomes 'id' (I can't justify this - if you can you should believe this answer much more).
'from' means one lot of letters go next to another.
'top' means to remove the first letter.
'to bottom' becomes 'sea' (sea bottom is a kind of bottom).
'sea' with its initial letter taken off is 'ea'.
'id'+'ea'='IDEA'
Can you help me to learn more?
(Other definitions for idea that I've seen before include "a wheeze" , "Clue" , "Plan" , "Notion, image" , "Mental impression" .)