A swimmer smoked something to divert the attention (3,7)
I believe the answer is:
red herring
'a swimmer' is the definition.
(red herring is a kind of fish)
'smoked something to divert the attention' is the wordplay.
I cannot quite see how this works, but
'something' could be 'er' (I've seen this in other clues) and 'er' is found in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for red herring that I've seen before include "Diversion intended to distract attention from the main issue" , "Distraction" , "It may well put you off" , "food?" , "Cover" .)