youve watched at least 2 productions of the play havent you? and your teachers supposed to have given you sheets on readings of the play and stuff.. at least my teacher did... btw does the question say its your own reading of the play??
just look at the notes on each version of lear that you watched (assuming you DID take notes) and see what type of interpretation suits you most
for example, my assessment was asking for my own interpretation of the play. I talked about the Richard Eyre's version of Lear and how it influenced my interpretation, because i think the play can be interpreted as a family drama through a psychoanalytical reading. blah blah
hope that helped at least a little bit
oh yeah, and if its a particular scene, the love test scene, the storm, and the very last scene are really good for several different readings