Gloomy nature's in trouble (9)
I believe the answer is:
saturnine
'gloomy' is the definition.
(I've seen this before)
'nature's in trouble' is the wordplay.
'trouble' indicates anagramming the letters.
'natures'+'in'='naturesin'
'naturesin' is an anagram of 'SATURNINE'.
(Other definitions for saturnine that I've seen before include "may be brooding" , "offering little amusement" , "Gloomy (temperament)" , "dour" , "Morose looking" .)