Fly low round southern desert (8)
I believe the answer is:
mosquito
'fly' is the definition.
(I've seen this before)
'low round southern desert' is the wordplay.
'low' becomes 'moo' (both can mean to make a cow noise).
'round' means one lot of letters goes inside another.
'southern' becomes 's' (abbreviation).
'desert' becomes 'quit' (I've seen this before).
's'+'quit'='squit'
'moo' going around 'squit' is 'MOSQUITO'.
(Other definitions for mosquito that I've seen before include "Kind of blood-sucking tropical gnat" , "Sucker" , "Malaria transmitter" , "Disease-carrying insect" , "Disease-spreading insect" .)