Fortunate girl about to finish work (5)
I believe the answer is:
lucky
'fortunate' is the definition.
('lucky' can be similar in meaning to 'fortunate')
'girl about to finish work' is the wordplay.
'girl' becomes 'lucy' (**).
'about' is an insertion indicator.
'to finish' suggests the final letters.
The final letter of 'work' is 'k'.
'lucy' going around 'k' is 'LUCKY'.
(Other definitions for lucky that I've seen before include "Auspicious" , "'It is better to be born . . . . . than rich'" , "Fortunate" , "Bringing good fortune" , "Blessed with good fortune" .)