I take a piece of bronze to be ferrous (4)
I believe the answer is:
iron
'ferrous' is the definition.
(I've seen this in another clue)
'i take a piece of bronze' is the wordplay.
I cannot really see how this works, but
'i' is present in the answer.
'take' could be 'r' (abbreviation for 'recipe', Latin for 'take') and 'r' is found within the answer.
'piece' could be 'n' (abbreviation for Knight in chess notation) and 'n' is present in the answer.
'of' could be 'o' and 'o' is found within the answer.
This accounts for all the letters.
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 iron that I've seen before include "resolve" , "A magnet attracts it" , "Main element in steel" , "Revolver" , "Hard metal" .)