Horny beast hurried over with young King Henry (7)
I believe the answer is:
narwhal
'horny beast' is the definition.
'narwhal' can be an answer for 'beast' (I've seen this before). I am not sure about the 'horny' bit.
'hurried over with young king henry' is the wordplay.
'hurried' becomes 'ran' (running is a kind of hurrying).
'over' is a reversal indicator.
'with young' becomes 'w' (I can't justify this - if you can you should give a lot more credence to this answer).
'king henry' becomes 'hal' (nickname of Henry V in Shakespeare's plays).
'ran' back-to-front is 'nar'.
'nar'+'w'+'hal'='NARWHAL'
Can you help me to learn more?
(Other definitions for narwhal that I've seen before include "swimmer" , "Cetacean with large tusk" , "Sea creature with a long spiral tusk" , "beast" , "Marine mammal with single tusk" .)