Take care of animal at emergency room (5)
I believe the answer is:
cater
'take care' is the definition.
Although both the answer and definition are verbs in their base form, I cannot see how one could define the other.
'animal at emergency room' is the wordplay.
'animal' becomes 'cat' (I've seen this before).
'at' is a charade indicator (letters next to each other).
'emergency room' becomes 'er' (abbreviation popularized by US TV series).
'cat'+'er'='CATER'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for cater that I've seen before include "Provide goods or services for" , "provide meals" , "Supply food for parties" , "Supply food and drink" , "Provide service for like grocer" .)