Nothing working for US president (5)
I believe the answer is:
nixon
'us president' is the definition.
(I've seen this before)
'nothing working' is the wordplay.
'nothing' becomes 'nix' ('nix' can be a synonym of 'zero').
'working' becomes 'on'.
'nix'+'on'='NIXON'
'for' acts as a link.
(Other definitions for nixon that I've seen before include "Only US president to have resigned from office" , "US president before Gerald Ford" , "37th president of the United States, resigned 1974" , "Politician" , "Watergate US president" .)