Pack animal appeared stern to girl (5)
I believe the answer is:
camel
'pack animal' is the definition.
'camel' can be an answer for 'animal' (I've seen this before). I am not sure about the 'pack' bit.
'appeared stern to girl' is the wordplay.
'appeared stern' becomes 'ca' (I can't explain this - if you can you should give a lot more credence to this answer).
'to girl' becomes 'Mel' (short for Melanie).
'ca'+'mel'='CAMEL'
Can you help me to learn more?
(Other definitions for camel that I've seen before include "Pale brown - animal" , "fawn" , "Humped beast" , "Beastly type" , "Ungulate mammal" .)