Thought to be perfect, though reduced by a pound (4)
I believe the answer is:
idea
'thought' is the definition.
(idea is a kind of thought)
'perfect though reduced by a pound' is the wordplay.
I cannot really understand how this works, but
'perfect' could be 'ide' (I've seen this in another clue) and 'ide' is found in the answer.
'a' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'to be' is the link.
Can you help me to learn more?
(Other definitions for idea that I've seen before include "Creative spark" , "Product of the mind" , "Fancy" , "Notion in the mind" , "It comes to mind" .)