Plot by alien to discover what we live on (6)
I believe the answer is:
planet
'discover what we live on' is the definition.
I can't judge whether this definition defines the answer.
'plot by alien' is the wordplay.
'plot' becomes 'plan' (plot can mean to conspire or plan).
'by' says to put letters next to each other.
'alien' becomes 'et' (extra terrestrial).
'plan'+'et'='PLANET'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for planet that I've seen before include "Substantial heavenly body" , "one of seven in suite" , "World" , "Eg, Mars, Venus" , "Jupiter is one" .)