Understood he'd one line in play from start to finish (2,3,8)
I believe the answer is:
go the distance
'finish' is the definition.
(I've seen this in another clue)
'understood he'd one line in play from start' is the wordplay.
'understood' becomes 'got' (getting is a kind of understanding).
'one' becomes 'i' (Roman numeral).
'line in play from start' becomes 'stance' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'got'+'hed'+'i'+'stance'='GO THE DISTANCE'
'to' is the link.
Can you help me to learn more?
(Other definitions for go the distance that I've seen before include "Complete a boxing match without being knocked out" , "Stay to finish" , "Stay the course" , "Complete job" , "finish off assignment" .)