Huge game of two halves, first to last (4)
I believe the answer is:
mega
'huge' is the definition.
(mega can mean very large)
'game of two halves first to last' is the wordplay.
'game' anagrams to 'MEGA'.
However, I am unsure how this is indicated.
Can you help me to learn more?
(Other definitions for mega that I've seen before include "ace" , "'Excellent, colloquially (4)'" , "Big" , "Huge (slang)" , "Great - denoting a million" .)