World's largest peninsula (6)
I believe the answer is:
arabia
'world's largest peninsula' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for arabia that I've seen before include "Peninsula between Red Sea and Persian Gulf" , "Asian peninsular" , "Area between Red Sea and Persian Gulf" , "'All the perfumes of ... will not sweeten this little hand' (Lady Macbeth)" , "Region between the Red Sea and Persian Gulf" .)