Southern crop (6)
I believe the answer is:
cotton
'southern crop' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cotton that I've seen before include "Soft white substance used to make fabric - in song, Old Man River don't plant it" , "Fabric (of natural fibre)" , "Natural textile fibre" , "Fabric made from tropical plant - old man river don't plant it" , "Cloth made from fine hairs of seed pod" .)