Terrible risk, including English athlete (5)
I believe the answer is:
skier
'athlete' is the definition.
(I know that skier is a type of athlete)
'terrible risk including english' is the wordplay.
'terrible' indicates an anagram.
'including' indicates putting letters inside.
'english' becomes 'E' (abbreviation as in OED).
'risk' with letters rearranged gives 'skir'.
'skir' going around 'e' is 'SKIER'.
(Other definitions for skier that I've seen before include "Slider on snow" , "Slalom contestant, perhaps" , "he's possibly going downhill quickly" , "sporting figure" , "Winter sportsman" .)