Two different pandas? One huge star! (3,5)
I believe the answer is:
red giant
'star' is the definition.
(I know that red giant is a type of star)
'two different pandas? one huge' is the wordplay.
'two different pandas? one' becomes 'red' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'huge' becomes 'giant' (I've seen this before).
'red'+'giant'='RED GIANT'
Can you help me to learn more?
(Other definitions for red giant that I've seen before include "Cool, immense star of high luminosity" , "Huge Communist" , "Type of star" , "Large star nearing the end of its life" , "Megastar" .)