The best part was getting the big score (4,5)
I believe the answer is:
high point
'the best part' is the definition.
(I've seen this before)
'getting the big score' is the wordplay.
I cannot quite understand how this works, but
'big' could be 'high' (synonyms) and 'high' is located in the answer.
'score' could be 'point' and 'point' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'was' is the link.
Can you help me to learn more?
(Other definitions for high point that I've seen before include "the best part?" , "The best bit" , "memorable occasion" , "Most successful time" .)