wni think the last leter is P
4 down's last lette may be the P you are inferring.
4 d is "part of the garden where leader slipsfree from restriction"
7 letters
U?S?R??
possibly unstrap or unstrip
cannot parse
you are right indeed about the theme.
refuse and detritus and garbage and litter feature.
it states solutions of a kind are underlined..
i dont see any underlining.