After half a day, openers can be animals (7)
I believe the answer is:
monkeys
'be animals' is the definition.
'after half a day openers can' is the wordplay.
'after' says to put letters next to each other.
'half a' means to take half the letters.
'day' becomes 'monday'.
'openers can' becomes 'keys' (I can't explain this - if you can you should give a lot more credence to this answer).
'monday' cut in half is 'mon'.
'mon' put next to 'keys' is 'MONKEYS'.
Can you help me to learn more?
(Other definitions for monkeys that I've seen before include "Long-tailed primates" , "What you get if you pay 14" .)