Somehow, the interior of Tithebarn House increased Robin’s unpleasant sensation of vertigo. No walls divided its vast interior. The first floor, which was reached by a steel and glass spiral staircase, was suspended on thick metal cables from the high ceiling. Chard’s huge double bed, which seemed to be of black leather, was visible, high above them, with what looked like a huge crucifix of barbed wire hanging over it on the brick wall. Robin dropped her gaze hastily, feeling sicker than ever.
(The Silkworm, by Robert Galbraith)
There is a relative word, which, which is the subject in the clause; and a fused relative phrase with what. What I would like to know is if you put a pause between ‘what’ and ‘looked.’ If ‘what’ can be a equivalent to ‘the thing that,’ in which ‘that’ would be a subordinator not a relative word (CGEL,p.1056). Then a gap would be the subject of 'looked' in ‘with the thing (i) that __ (i) looked like a huge crucifix.’ So recently I pause whenever I happen to come across 'what' fused relative phrases. Is my view proper?