Short hair on balls goes astray (10)
I believe the answer is:
trespasses
'goes astray' is the definition.
'short hair on balls' is the wordplay.
'short' means to remove the last letter.
'hair' becomes 'tress' (tress is a kind of hair).
'on balls' becomes 'passes' (I am not sure about this - if you are sure you should believe this answer much more).
'tress' with its final letter taken away is 'tres'.
'tres'+'passes'='TRESPASSES'
Can you help me to learn more?
(Other definitions for trespasses that I've seen before include "Forgive them" , "may they be forgiven!" , "Unlawfully enters" .)