Plan beginning to disappoint large number (5)
I believe the answer is:
Here is my best explanation:
'plan' is the definition.
(drafting is a kind of planning)
'beginning to disappoint large number' is the wordplay.
'beginning to' suggests taking the first letters.
'large number' becomes 'raft' (I can't explain this - if you can you should believe this answer much more).
The first letter of 'disappoint' is 'd'.
(Other definitions for draft that I've seen before include "plan outlined", "Send", "Formulate", "Outline or sketch", "Bank payment order", "Money order", "Preliminary text or plan", "form of conscription", "Early version of text" and "Sketch; money order".)