He drafted one hot design but that was as far as he could go (3,3,2,3,4)
I believe the answer is:
the end of the road
'that was as far as he could go' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'he drafted one hot design' is the wordplay.
'design' is an anagram indicator.
'he'+'drafted'+'one'+'hot'='hedraftedonehot'
'hedraftedonehot' with letters rearranged gives 'THE END OF THE ROAD'.
'but' is the link.
Can you help me to learn more?
(Other definitions for the end of the road that I've seen before include "The last possible point (3,3,2,3,4)" , "Final situation" , "when we all learn to fly?" , "Point beyond which one can't go (3,3,2,3,4)" , "curtains" .)