Woman with aim to ensnare one (4)
I believe the answer is:
enid
'woman' is the definition.
(woman's name)
'aim to ensnare one' is the wordplay.
'aim' becomes 'end' (both can mean a goal or purpose).
'to ensnare' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'end' enclosing 'i' is 'ENID'.
'with' acts as a link.
(Other definitions for enid that I've seen before include "Writer of children's books, d. 1968" , "Dine out on this girl's name also" , "Miss Blyton" , "Woman" , "- Blyton, twentith century writer" .)