Make bubbly that's consumed over a long time (6)
I believe the answer is:
aerate
'make bubbly' is the definition.
(aerate can mean to make something bubbly)
'consumed over a long time' is the wordplay.
'consumed' becomes 'ate' (eating is a kind of consuming).
'over' is an insertion indicator.
'a long time' becomes 'era' (a long period of time).
'ate' enclosing 'era' is 'AERATE'.
'that's' acts as a link.
(Other definitions for aerate that I've seen before include "Supply with oxygen" , "produce inflation?" , "get excited" , "Introduce gas to" , "Get bubbly" .)