Slough hospital is after damages (5)
I believe the answer is:
marsh
'slough' is the definition.
(thesaurus)
'hospital is after damages' is the wordplay.
'hospital' becomes 'h'.
'is after' means one lot of letters go next to another.
'damages' becomes 'mars' (marring is a kind of damaging).
'h' after 'mars' is 'MARSH'.
(Other definitions for marsh that I've seen before include "Low-lying wet land with grassy vegetation" , "Wetland" , "Wet land; swamp" , "Swampy ground" , "Waterlogged land" .)