One of the top three celebs touring lake next to the sea (9)
I believe the answer is:
medallist
'one of the top three' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'celebs touring lake next to the sea' is the wordplay.
'celebs' becomes 'alist' (I have seen 'Top celebs' mean 'a list' so perhaps 'celebs' could also mean 'a list').
'touring' indicates putting letters inside (touring can mean going round).
'lake' becomes 'l'.
'next to' says to put letters next to each other.
'the sea' becomes 'med' (short for Mediterranean).
'alist' placed around 'l' is 'allist'.
'allist' after 'med' is 'MEDALLIST'.
Can you help me to learn more?
(Other definitions for medallist that I've seen before include "Prizewinner" , "Award winner" , "Olympic winner" , "Successful sportsperson" .)