Incapable of sustaining life (6)
I believe the answer is:
barren
'incapable of sustaining life' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for barren that I've seen before include "Not producing vegetation or offspring" , "Unable to bear fruit, not fertile" , "Incapable of sustaining life" , "Infertile, unable to grow things" , "Arid of unfertile" .)