Big game shot (4)

I believe the answer is:

mega

'big' is the definition.
(I've seen this before)

'game shot' is the wordplay.
'shot' indicates an anagram.
'game' is an anagram of 'MEGA'.

(Other definitions for mega that I've seen before include "Great American" , "Smashing" , "ace" , "Informally great or large" , "Game (anag) -- great" .)

I've seen this clue in The Telegraph.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.