Red Sea supports swimming final (8)
I believe the answer is:
inflamed
'red' is the definition.
(synonyms)
'sea supports swimming final' is the wordplay.
'sea' becomes 'med' (short for Mediterranean).
'supports' means one lot of letters go next to another (bottom letters provide a support for the top ones).
'swimming' indicates anagramming the letters (letters swim around into a new order).
'final' with letters rearranged gives 'infla'.
'med' put after 'infla' is 'INFLAMED'.
(Other definitions for inflamed that I've seen before include "Aggravated; red" , "Swollen, hot, red" , "Angry" , "one so hot and bothered" , "Red and sore" .)