British steed sadly got defeated (6)
I believe the answer is:
bested
'defeated' is the definition.
(similar in meaning)
'british steed sadly' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in BBC).
'sadly' is an anagram indicator.
'steed' with letters rearranged gives 'ested'.
'b'+'ested'='BESTED'
'got' is the link.
(Other definitions for bested that I've seen before include "Worsted" , "Conquered, overcame" , "Defeated or outwitted" .)