When I add a great deal of land (4)
I believe the answer is:
asia
'a great deal of land' is the definition.
(I've seen this before)
'when i add' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'i add' becomes 'ia' (this might be a standard abbreviation of which I'm unaware).
'as'+'ia'='ASIA'
Can you help me to learn more?
(Other definitions for asia that I've seen before include "A great deal of land" , "A vast number of people have lived here" , "It has most of the earth's population" , "The nations of the East, collectively" , "its pampered jades couldn't draw much?" .)