Athlete wires about getting married twice (7)
I believe the answer is:
swimmer
'athlete' is the definition.
(I know that swimmer is a type of athlete)
'wires about getting married twice' is the wordplay.
'about' indicates an anagram.
'getting' indicates putting letters inside.
'married' becomes 'm'.
'twice' shows that letters should be duplicated.
'wires' anagrammed gives 'swier'.
'm' duplicated is 'mm'.
'swier' placed around 'mm' is 'SWIMMER'.
(Other definitions for swimmer that I've seen before include "Michael Phelps, say" , "One doing crawl, say" , "Eg, Captain Webb" , "fish" , "A mover in water" .)