Soon, at nine about, mother will enter (2,1,6)
I believe the answer is:
in a moment
'soon' is the definition.
(synonyms)
'at nine about mother will enter' is the wordplay.
'about' indicates an anagram.
'mother will' becomes 'mom' (I can't explain this - if you can you should give a lot more credence to this answer).
'enter' indicates putting letters inside.
'at'+'nine'='atnine'
'atnine' is an anagram of 'inaent'.
'inaent' enclosing 'mom' is 'IN A MOMENT'.
Can you help me to learn more?
(Other definitions for in a moment that I've seen before include "shortly" , "Soon" .)