Being an expert swimmer is a bit of a lottery (5)
I believe the answer is:
otter
'being an expert swimmer is a bit' is the definition.
I can't judge whether this definition defines the answer.
'of a lottery' is the wordplay.
'of' says the answer is hidden in the clue.
'OTTER' is hidden within 'lottery'.
Can you help me to learn more?
(Other definitions for otter that I've seen before include "Web-footed mammal" , "Carnivorous aquatic mammal" , "Holt dweller" , "Freshwater brown carnivore" , "Good swimmer" .)