Farm hand is constant female with lowered head (6)
I believe the answer is:
cowman
This might be a double definition.
'farm hand' is the first definition.
'constant female with lowered head' is the second definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'is' is the link.
(Other definitions for cowman that I've seen before include "Tender of cattle" , "Stocky chap" .)