Sweet desert animal with a leading role (7)
I believe the answer is:
caramel
'sweet' is the definition.
(caramel is a kind of sweet)
'desert animal with a leading role' is the wordplay.
'desert animal' becomes 'camel' (I've seen this before).
'with' is an insertion indicator.
'leading' indicates taking the first letters.
The initial letter of 'role' is 'r'.
'a'+'r'='ar'
'camel' enclosing 'ar' is 'CARAMEL'.
(Other definitions for caramel that I've seen before include "Sugar solution heated till brown" , "Soft toffee" , "Toffee-like sweet" , "Shade" , "Chewy sweet - burnt sugar" .)