Diplomat shows downside with those leading such unhealthy lives (6)
I believe the answer is:
consul
'diplomat' is the definition.
(I know that consul is a type of diplomat)
'downside with those leading such unhealthy lives' is the wordplay.
'downside' becomes 'con' (I've seen this in another clue).
'with' says to put letters next to each other.
'those leading' indicates taking the first letters (the letters which lead the words).
The initial letters of 'such unhealthy lives' is 'sul'.
'con'+'sul'='CONSUL'
'shows' acts as a link.
(Other definitions for consul that I've seen before include "Diplomat abroad" , "Chief magistrate in ancient Rome" , "Ambassador" , "Magistrate in ancient Rome or modern diplomat" , "Roman chief magistrate" .)