Old scientist has crime heads confused (10)
I believe the answer is:
archimedes
'old scientist' is the definition.
(I've seen this before)
'crime heads confused' is the wordplay.
'confused' indicates an anagram.
'crime'+'heads'='crimeheads'
'crimeheads' anagrammed gives 'ARCHIMEDES'.
'has' acts as a link.
(Other definitions for archimedes that I've seen before include "Greek mathematician ('Eureka')" , "Old mathematician" , "Syracusan" , "Ancient Greek scientist (of buoyancy principle)" , "Greek physicist" .)