Many intend to do physical harm (4)
I believe the answer is:
maim
'harm' is the definition.
(to maim is to harm or injure)
'many intend' is the wordplay.
'many' becomes 'm' (Roman numeral for a thousand).
'intend' becomes 'aim' (aiming is a kind of intending).
'm'+'aim'='MAIM'
'to do physical' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for maim that I've seen before include "Wound or injure, disable" , "Injure seriously, leaving permanent damage" , "'Disable, mutilate (4)'" , "Wound and permanently disfigure" , "Injure (a person), causing permanent disability" .)