Unexpected streak for sportsman (6)
I believe the answer is:
skater
'for sportsman' is the definition.
(eg an ice-skater)
'unexpected streak' is the wordplay.
'unexpected' indicates anagramming the letters.
'streak' is an anagram of 'SKATER'.
(Other definitions for skater that I've seen before include "One moving over ice" , "One sliding over ice" , "One moves on ice" , "Dean, perhaps" , "Winter sports person" .)