Buddy stops after short day (7)
I believe the answer is:
friends
'buddy stops after short day' is the definition.
I can't judge whether this definition defines the answer.
'stops after short day' is the wordplay.
'stops' becomes 'ends' ('end' can be a synonym of 'stop').
'after' means one lot of letters go next to another.
'short day' becomes 'fri' (abbreviation for Friday; 'short' indicates a short form).
'ends' after 'fri' is 'FRIENDS'.
Can you help me to learn more?
(Other definitions for friends that I've seen before include "Intimate acquaintances" , "Intimates" , "Chums" , "''..., Romans, countrymen, lend me your ears'' (Julius Caesar)" , "American sitcom" .)