Old British ruined castle, something standing in the way of progress (8)
I believe the answer is:
obstacle
'something standing in the way of progress' is the definition.
I can't judge whether this definition defines the answer.
'old british ruined castle' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'ruined' is an anagram indicator.
'castle' anagrammed gives 'stacle'.
'o'+'b'+'stacle'='OBSTACLE'
Can you help me to learn more?
(Other definitions for obstacle that I've seen before include "A spanner in the works?" , "Block to progress" , "Barrier or deterrent" , "bar" , "race" .)