She’s short of salt (3)
I believe the answer is:
sal
'salt' is the definition.
(I've seen this in other clues)
'she's short of' is the wordplay.
'she's' becomes 'sals'.
'short of' means to remove the last letter (I've seen 'short' mean this).
'sals' with its last letter removed is 'SAL'.
(Other definitions for sal that I've seen before include "Sarah (dim.)" , "girl?" , "- - volatile" .)