The beastly one in Hamlet? (5,4)
I believe the answer is:
Here is my best explanation:
'the beastly one in hamlet?' is the definition.
'great dane' can be an answer for 'hamlet?' (I've seen this before). I am not sure about the 'the beastly one in' bit.
'in hamlet?' is the subsidiary indication.
'in' becomes 'great' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'hamlet?' becomes 'dane' (Hamlet is a famous Dane).
(Other definitions for great dane that I've seen before include "Dog -- a tad green (anag)", "Powerful dog", "Large breed of dog", "Hamlet possibly", "Pet", "Kierkegaard, perhaps?", "Big dog", "Very large dog", "Large 11" and "one among best friends".)