Back in a little while (6)
I believe the answer is:
second
This clue is a double definition.
'back' is the first definition.
(both can mean to support an idea or proposal)
'a little while' is the second definition.
(I've seen this before)
'in' acts as a link.
(Other definitions for second that I've seen before include "Formally support, endorse" , "Short-lived" , "Endorse, back" , "Behind" , "Not first team (6,6) - See 25" .)