Smoking not good for diver (6)
I believe the answer is:
puffin
'diver' is the definition.
(I've seen this before)
'smoking not good' is the wordplay.
'smoking' becomes 'puffing' (puffing is a kind of smoking).
'not' indicates named letters should be taken away.
'good' becomes 'g' (abbreviation).
'puffing' with 'g' taken away is 'PUFFIN'.
'for' is the link.
(Other definitions for puffin that I've seen before include "Northern seabird with short neck and brightly coloured bill" , "Bright-beaked sea bird" , "Bird with large beak" , "diver" , "Large-beaked sea bird" .)