Ted's worried about European mount (5)
I believe the answer is:
steed
'mount' is the definition.
(I've seen this before)
'ted's worried about european' is the wordplay.
'worried' indicates an anagram.
'about' means one lot of letters goes inside another.
'european' becomes 'e' (abbreviation e.g. EU).
'teds' anagrammed gives 'sted'.
'sted' enclosing 'e' is 'STEED'.
(Other definitions for steed that I've seen before include "Spirited horse" , "Stallion" , "Trusty horse" , "Warhorse" , "ride" .)