Pronoun all but dropped (3)
I believe the answer is:
she
'pronoun' is the definition.
(I've seen this before)
'all but dropped' is the wordplay.
'all but' means to remove the last letter ('all but' can mean 'almost' or 'nearly').
'dropped' becomes 'shed' ('shed' can be a synonym of 'drop').
'shed' with its final letter removed is 'SHE'.
(Other definitions for she that I've seen before include "Female person" , "The one who must be obeyed" , "1887 Rider Haggard novel" , "Rider's novel" , "Female pronoun" .)