Soon makes the girl duck inside (4)
I believe the answer is:
anon
'soon' is the definition.
(synonyms)
'the girl duck inside' is the wordplay.
'the girl' becomes 'ann' (woman's name).
'duck' becomes 'o' (resembles zero - 'duck' in cricket).
'inside' means one lot of letters goes inside another.
'ann' enclosing 'o' is 'ANON'.
'makes' acts as a link.
(Other definitions for anon that I've seen before include "In due course" , "Shortly; unknown" , "Soon; unnamed" , "Mystery writer" , "soon to be written" .)