Legendary king put girl's name in manuscript (5)
I believe the answer is:
midas
'legendary king' is the definition.
(I've seen this before)
'girl's name in manuscript' is the wordplay.
'girl's name' becomes 'ida' ().
'in' means one lot of letters goes inside another.
'manuscript' becomes 'ms' (abbreviation for manuscript).
'ida' placed within 'ms' is 'MIDAS'.
'put' acts as a link.
(Other definitions for midas that I've seen before include "Legendary king whose touch turned anything to gold" , "Mythical king with golden touch" , "His touch made gold" , "Legendary king with golden touch" , "old king" .)