Large landmass like India and America (4)
I believe the answer is:
asia
'large landmass' is the definition.
(I've seen this in another clue)
'like india and america' is the wordplay.
'like' becomes 'as'.
'india' becomes 'i' (phonetic alphabet: alpha, bravo, charlie etc.).
'and' says to put letters next to each other.
'america' becomes 'a' (common abbreviation - e.g. in organisation names).
'as'+'i'+'a'='ASIA'
(Other definitions for asia that I've seen before include "huge territory" , "Continent in which India is situated" , "One-third of all land" , "Stretch of land" , "space for economic expansion?" .)