Soon girl must get round in (4)
I believe the answer is:
anon
'soon' is the definition.
(synonyms)
'girl must get round in' is the wordplay.
I cannot quite see how this works, but
'round' could be 'o' (round can mean a round object) and 'o' is found in the answer.
'girl' could be 'ann' (woman's name) and 'ann' is located in the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for anon that I've seen before include "Presently - unattributed" , "In a little while (informal)" , "Presently - or unknown" , "Writer unknown" , "Nameless - presently" .)