Back end of chestnut horse given stroke (9)
I believe the answer is:
punchline
'back end' is the definition.
'punchline' can be an answer for 'end' (I have seen 'end of story' mean 'punchline' so perhaps 'end' could also mean 'punchline'). I'm unsure of the 'back' bit.
'chestnut horse given stroke' is the wordplay.
'chestnut horse' becomes 'punch' (type of horse. I am not sure about the 'chestnut' bit.).
'given' says to put letters next to each other.
'stroke' becomes 'line' (stroke can mean a line or bar).
'punch'+'line'='PUNCHLINE'
'of' is the link.
Can you help me to learn more?
(Other definitions for punchline that I've seen before include "This should make you laugh" , "Gag's ending" , "one is expected to laugh at" , "end of story" , "bit of a joke" .)