Sport in lake with mist rising round (4)
I believe the answer is:
golf
'sport' is the definition.
(golf is a kind of sport)
'lake with mist rising round' is the wordplay.
'lake with' becomes 'l' (I can't explain this - if you can you should give a lot more credence to this answer).
'mist' becomes 'fog' (synonyms).
'rising' is a reversal indicator (going up in a down clue).
'round' means one lot of letters goes inside another.
'fog' backwards is 'gof'.
'l' going inside 'gof' is 'GOLF'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for golf that I've seen before include "Game on greens" , "To some, it's a good walk spoiled" , "Game involving woods and irons" , "Irons and woods sport" , "a round or two?" .)