Mingle during period before nine (8)
I believe the answer is:
intermix
'mingle' is the definition.
(intermixing is a kind of mingling)
'during period before nine' is the wordplay.
'during' becomes 'in' (e.g. during February means in February).
'period' becomes 'term' (term is a kind of period).
'before' says to put letters next to each other.
'nine' becomes 'IX' (roman numeral).
'in'+'term'+'ix'='INTERMIX'
(Other definitions for intermix that I've seen before include "Blend together" , "Stir" , "Mingle" .)