I needed help to solve it, but I would still say it's a perfect clue. You need to understand that light is a synonym for window (cf skylight and fanlight). So "fitting light" can be interpreted as "fitting a window" or "glazing".
I struggled with "in middle of". It's deliberately misleading, but correct. It doesn't mean you should put the extra letter G in the middle. Rather that when you are lazing you are "in the middle of [a] lounge".
I'm impressed with the skills of those that did solve it.