Heard about unpopular cider from a stranger (8)
I believe the answer is:
outsider
'cider from a stranger' is the definition.
'outsider' can be an answer for 'stranger' (outsider is a kind of stranger). I'm not sure about the 'cider from a' bit.
'heard about unpopular' is the wordplay.
'heard' becomes 'sider' (I can't justify this - if you can you should believe this answer much more).
'about' says to put letters next to each other.
'unpopular' becomes 'out' (similar in meaning).
'sider' put after 'out' is 'OUTSIDER'.
Can you help me to learn more?
(Other definitions for outsider that I've seen before include "One not in a particular group" , "Not one of the favourites" , "Someone not accepted by society" , "Stranger" , "One who doesn't belong (or isn't fancied)" .)