Sailing vessel, round, found in sports club (4)
I believe the answer is:
boat
'sailing vessel' is the definition.
(sailing boat)
'round found in sports club' is the wordplay.
'round' becomes 'o' (o is a circular letter).
'found in' indicates putting letters inside.
'sports club' becomes 'bat' (I've seen this in another clue).
'o' inserted within 'bat' is 'BOAT'.
(Other definitions for boat that I've seen before include "See 18" , "Floating vessel" , "Water transport" , "Small ship" , "Eg, coracle" .)