Heartless type shot big game (4)
I believe the answer is:
test
'big game' is the definition.
(I've seen this before)
'heartless type shot' is the wordplay.
'heartless' suggests removing the centre.
'shot' becomes 'st' (I can't explain this - if you can you should believe this answer much more).
'type' with its middle removed is 'te'.
'te'+'st'='TEST'
(Other definitions for test that I've seen before include "big game" , "Ward off" , "Examine to play international cricket match" , "Audition" , "Try, examine critically" .)