Cross channel swimmer not covered in fat rejected warning to stop (7)
I believe the answer is:
Here is my best explanation:
'cross channel swimmer' is the definition.
'leander' can be an answer for 'swimmer' (I've seen this before). I'm not sure about the 'cross channel' bit.
I cannot understand how the rest of the clue works.
(Other definitions for leander that I've seen before include "Hero's lover; rowing club", "Learned Greek lover who swam Hellespont to meet Hero", "Lover who swam the Hellespont to Hero", "youth who drowned", "Tragic Greek", "In Greek legend, lover of Hero who drowned in the Hellespont", "Heroic lover", "In Greek mythology, Hero's beloved who drowned in a lake", "man who went under" and "He swam for love".)