Agreed to smash one of the old gods that screw man (10)
I believe the answer is:
archimedes
'man' is the definition.
(I have seen 'Man of principle' mean 'archimedes' so perhaps 'man' could also mean 'archimedes')
'agreed to smash one of the old gods that screw' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'me' (a setter might use 'one' to humourously mean 'me') and 'me' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for archimedes that I've seen before include "Ancient Greek mathematician/inventor" , "Ancient Greek scientist (of buoyancy principle)" , "Old mathematician" , "Greek mathematician and inventor" , "Greek physicist" .)