Chief means of support (4)
I believe the answer is:
arch
This might be a double definition.
'chief' is the first definition.
(synonyms)
'of support' is the second definition.
'arch' can be an answer for 'support'. I'm unsure of the 'of' bit.
'means' acts as a link.
Can you help me to learn more?
(Other definitions for arch that I've seen before include "Prefix meaning cheif, perhaps enemy" , "Curve of a bridge" , "Chief: crafty" , "Bend into upward curve" , "Devilish" .)