Girl going round a hot desert (6)
I believe the answer is:
sahara
'desert' is the definition.
(I know that Sahara is a desert)
'girl going round a hot' is the wordplay.
'girl' becomes 'sara' (girl's name).
'going round' means one lot of letters goes inside another (some letters go around others).
'hot' becomes 'h' (abbreviation eg on taps).
'a'+'h'='ah'
'sara' going around 'ah' is 'SAHARA'.
(Other definitions for sahara that I've seen before include "Uncultivated region of north Africa" , "Great African desert" , "Great desert in N Africa" , "Hottest desert" , "World's largest desert" .)