Lines up an alternative projection of earth (9)
I believe the answer is:
peninsula
'projection of earth' is the definition.
'peninsula' can be an answer for 'earth' (peninsula is a kind of earth). I'm not sure about the 'projection of' bit.
'lines up an alternative' is the wordplay.
'alternative' is an anagram indicator.
'lines'+'up'+'an'='linesupan'
'linesupan' anagrammed gives 'PENINSULA'.
Can you help me to learn more?
(Other definitions for peninsula that I've seen before include "Piece of land projecting into water" , "land project" , "Lower California, say" , "Land mostly surrounded by water" , "Malay for one" .)