Has raised Bedouin, say, mostly in desert (6)
I believe the answer is:
sahara
'desert' is the definition.
(I've seen this before)
'has raised bedouin say mostly' is the wordplay.
'raised' says the letters should be written backwards.
'bedouin say' becomes 'arab' (bedouin is a kind of Arab).
'mostly' means to remove the last letter.
'has' written backwards gives 'sah'.
'arab' with its last letter taken away is 'ara'.
'sah'+'ara'='SAHARA'
'in' is the link.
(Other definitions for sahara that I've seen before include "About 3,500,000 square miles of Africa" , "Hottest desert" , "Great desert in N Africa" , "Great African desert" , "World's largest desert" .)