Hand book, say, to leading lady (6)
I believe the answer is:
worker
'hand' is the definition.
(thesaurus)
'book say to leading lady' is the wordplay.
'book say' becomes 'work' (book is a kind of work).
'to leading lady' becomes 'er' (Elizabeth Regina).
'work'+'er'='WORKER'
(Other definitions for worker that I've seen before include "See 8" , "See 20" , "Manual employee" , "Busy bee" , "Labourer" .)