Begrudge diplomat lacking nothing (4)
I believe the answer is:
envy
'begrudge' is the definition.
('envy' can be a synonym of 'begrudge')
'diplomat lacking nothing' is the wordplay.
'diplomat' becomes 'envoy' (envoy is a kind of diplomat).
'lacking' is a deletion indicator.
'nothing' becomes 'o' (looks like zero - 0).
'envoy' with 'o' taken out is 'ENVY'.
(Other definitions for envy that I've seen before include "One of seven deadly sins" , "Jealous longing" , "Covetousness" , "Jealousy, resentment" , "Green-eyed feeling" .)