Covetousness of emissary lacking nothing (4)
I believe the answer is:
envy
'covetousness' is the definition.
(thesaurus)
'emissary lacking nothing' is the wordplay.
'emissary' becomes 'envoy' ('envoy' can be a synonym of 'emissary').
'lacking' suggests deleting specific letters.
'nothing' becomes 'o' (looks like zero - 0).
'envoy' with 'o' removed is 'ENVY'.
'of' is the link.
(Other definitions for envy that I've seen before include "Resentment at another's success" , "The green-eyed monster" , "One of 7 vices" , "The green-eyed emotion" , "One of the 7 deadly sins" .)