Lifeless backup covering Republican (4)
I believe the answer is:
arid
'lifeless' is the definition.
(I've seen this in another clue)
'backup covering republican' is the wordplay.
'backup' becomes 'aid' (backup is aid or assistance).
'covering' is an insertion indicator.
'republican' becomes 'R' (political abbreviation).
'aid' placed around 'r' is 'ARID'.
(Other definitions for arid that I've seen before include "Desiccated" , "Parched and barren" , "Parched, waterless" , "Sterile" , "Parched with heat" .)