Composer last seen in wet Sussex resort has called round (9)
I believe the answer is:
beethoven
'composer' is the definition.
(Beethoven is an example)
'last seen in wet sussex resort has called round' is the wordplay.
'last seen in' indicates one should take the final letters.
'sussex resort' becomes 'hove' (seaside resort in Sussex).
'has' is a charade indicator (letters next to each other).
'called' becomes 'been' (both can mean visited).
'round' indicates putting letters inside.
The last letter of 'wet' is 't'.
't'+'hove'='thove'
'thove' going within 'been' is 'BEETHOVEN'.
(Other definitions for beethoven that I've seen before include "German barman" , "Ludwig van . . . . . . . . ., immortal German composer 1770-1827 (9)" , "I composed" , "source of bars?" , "Pastoral Symphony composer, d. 1827" .)