Eccentric person following big game producing visual chart (4,4)
I believe the answer is:
test card
'visual chart' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'eccentric person following big game' is the wordplay.
'eccentric person' becomes 'card' (card can informally mean an eccentric).
'following' says to put letters next to each other.
'big game' becomes 'test' (I've seen this before).
'card' put after 'test' is 'TEST CARD'.
'producing' is the link.
Can you help me to learn more?
(Other definitions for test card that I've seen before include "Cricket scoring system" , "what's not usually watched on TV" , "shown on TV in an idle moment?" , "Detailed pattern for checking TV picture" .)