Falling behind with insulation (7)
I believe the answer is:
lagging
I believe this is a double definition.
'falling behind' is the first definition.
('lag' can be a synonym of 'fall behind')
'insulation' is the second definition.
(I know that lagging is a type of insulation)
'with' is the link.
(Other definitions for lagging that I've seen before include "It's used to wrap around boilers, say, to prevent heat-loss" , "Insulating material" , "Insulation -- failing to keep up" , "job in the attic?" , "Not up to date" .)