Leading lady on needy cast (7)
I believe the answer is:
doyenne
'leading lady' is the definition.
(I've seen this in another clue)
'on needy cast' is the wordplay.
'cast' indicates anagramming the letters (letters are dispersed or cast around).
'on'+'needy'='onneedy'
'onneedy' is an anagram of 'DOYENNE'.
(Other definitions for doyenne that I've seen before include "Senior female member of profession" , "Yon Eden (anag.)" , "An older academic" , "Senior female member of a group" , "Respected lady" .)