Man of stone (6)
I believe the answer is:
jasper
This clue is a double definition.
'man' is the first definition.
(I have seen 'A man' mean 'jasper' so perhaps 'man' could also mean 'jasper')
'stone' is the second definition.
(I've seen this before)
'of' is the link.
(Other definitions for jasper that I've seen before include "Semi-precious quartz stone -- boy's name" , "Opaque quartz" , "hard matter" , "A man" , "Reddish-brown stone used in jewellery" .)