Racket around old vessel (4)
I believe the answer is:
boat
'vessel' is the definition.
(I know that boat is a type of vessel)
'racket around old' is the wordplay.
'racket' becomes 'bat' (bat is a kind of racket).
'around' indicates putting letters inside.
'old' becomes 'o' (abbreviation).
'bat' placed around 'o' is 'BOAT'.
(Other definitions for boat that I've seen before include "See 12 Down" , "Contest on the Thames" , "Small ship" , "Water (or gravy) vessel" , "Water transport" .)