In the role of Lear, perhaps, which is demanding (6)
I believe the answer is:
asking
'is demanding' is the definition.
(I've seen this before)
'in the role of lear perhaps' is the wordplay.
'in the role of' becomes 'as' (as in an actor appearing as a character).
'lear perhaps' becomes 'king' (I can't explain this - if you can you should give a lot more credence to this answer).
'as'+'king'='ASKING'
'which' is the link.
Can you help me to learn more?
(Other definitions for asking that I've seen before include "Making enquiries" , "Making request" , "Proposing" , "Inviting (to an event)" , "Putting question or requesting" .)