Put aside large building designed primarily to support farm animals (10)
I believe the answer is:
stockpiled
'farm animals' is the definition.
The answer and definition are different parts of speech. However, past participle verbs and adjectives occasionally mean the same thing.
'put aside large building designed primarily to support' is the wordplay.
'put aside' becomes 'stock' (I can't explain this - if you can you should give a lot more credence to this answer).
'large building' becomes 'pile' (I've seen this before).
'primarily' indicates taking the first letters.
'to support' is a charade indicator (letters next to each other) (in a down clue, some letters hold others up).
The initial letter of 'designed' is 'd'.
'stock'+'pile'+'d'='STOCKPILED'
Can you help me to learn more?
(Another definition for stockpiled that I've seen is " hoarded".)