Bug has green lip shortened (1,4)
I believe the answer is:
e coli
'bug' is the definition.
(I've seen this before)
'green lip shortened' is the wordplay.
'green' becomes 'eco' (abbreviation for ecological).
'shortened' means to remove the last letter.
'lip' with its final letter removed is 'li'.
'eco'+'li'='E COLI'
'has' acts as a link.
(Other definitions for e coli that I've seen before include "Bacterium found in the gut" , "Nasty bug" , "cause of illness" , "Some types of this bacterium are toxic" , "cause of serious complaint" .)