Ted's worried about European horse (5)
I believe the answer is:
steed
'horse' is the definition.
(steed is a kind of horse)
'ted's worried about european' is the wordplay.
'worried' indicates an anagram (worry can mean to interfere with or disturb).
'about' indicates putting letters inside.
'european' becomes 'E' (abbreviation e.g. EU).
'teds' is an anagram of 'sted'.
'sted' going around 'e' is 'STEED'.
(Other definitions for steed that I've seen before include "Horse, mount" , "Stallion" , "ride" , "A mount (poet.)" , "Spirited horse" .)