Barren aliens over anger (7)
I believe the answer is:
sterile
'barren' is the definition.
(I've seen this in another clue)
'aliens over anger' is the wordplay.
'aliens' becomes 'ETs' (ET is short for extraterrestrial).
'over' is a reversal indicator.
'anger' becomes 'rile' (rile can mean to annoy or anger).
'ets' written backwards gives 'ste'.
'ste'+'rile'='STERILE'
(Other definitions for sterile that I've seen before include "Not producing offspring" , "Unable to have children" , "Ineffective" , "Germ-free" , "Incapable of reproducing" .)