Heading for ditch, pal knocked from top of horse -- faller in effect? (6)
I believe the answer is:
domino
'heading for ditch pal knocked' is the definition.
I can't tell whether this definition defines the answer.
'top of horse faller in effect?' is the wordplay.
'top' indicates taking the first letters.
'horse faller' becomes 'min' (I am not sure about this - if you are sure you should believe this answer much more).
'in' means one lot of letters goes inside another.
'effect?' becomes 'do' (effecting is a kind of doing).
The initial letter of 'of' is 'o'.
'o'+'min'='omin'
'omin' inserted into 'do' is 'DOMINO'.
'from' acts as a link.
Can you help me to learn more?
(Other definitions for domino that I've seen before include "Playing piece; cloak" , "one coming down with many others?" , "Piece with pips; Fats ---, R&B singer" , "Officers' mess aboard" , "Black and white game piece" .)